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klm672
Topic Author
Posts: 2563
Joined: Mon Oct 04, 1999 6:09 am

### I Need A Little Help With Math

Hello. I have a math assestment coming up with a mixture of problems including percents, discounts, world problems, graphs, alegbra and probablility. I was wondering if anyone thats pretty good at math and good at teaching/explaining is willing to shoot e-mails back and fourth to help me. There are only about 20-25 problems. I've googled and unfourntally I dont have a math textbook around.
Thanks so much
Please email me: [email protected]

-Andre

RGElectra80
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### RE: I Need A Little Help With Math

austinspotter.wordpress.com

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### RE: I Need A Little Help With Math

Why not just post them here?

klm672
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### RE: I Need A Little Help With Math

I thought people might not like posting it on here. I could, if everyone thinks thats ok?

Mir
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### RE: I Need A Little Help With Math

 Quoting KLM672 (Thread starter):I have a math assestment coming up with a mixture of problems including percents, discounts, world problems,

That sounds like some pretty advanced math.

Put them up on the thread and see what answers you get.

-Mir
7 billion, one nation, imagination...it's a beautiful day

klm672
Topic Author
Posts: 2563
Joined: Mon Oct 04, 1999 6:09 am

### RE: I Need A Little Help With Math

hahha opps..
These are from the sample test I've taken online which reveals the answers (the are in ( ) following the question at the end. I'd like you to show me how you solved it and if you can give me a similar problem for practice (to make sure I get the concept and can do similar problems on the real test). I am not here just for the answers

Here ya go:
On a blueprint, 1/4 inch represents 16 feet. If a drive way is 40 feet long, what is its length, in inches, on the map? (5/8)

A rabbit grows so that every 2 months it doubles in weight. However, the rabbit will never go over 75 lbs. If a bunny if born on July 15th weighing 2 lbs, in which month will it weight 46 lbs? (April)

If a person puts 1 Cent in a piggy bank on the first day, 2 cents on the second, 3 cents on the third etc, how much money will be in the bank after 50 days? (\$12.75)

On a map, the length of a nature-center trail is 9.7 centimeters. If the scale is 3 centimeters to 25 kilometers, what is the actual length of the trail? (80.8 Kilometers)

In a sale, the prices of a computer is reduced from \$1280 to \$1030. Find the discount and the rate of discount. Round the discount rate to the nearest tenth of a percent if necessary. I got the discount which is \$250 = 1280-1030=250 but I am not sure how to do figure out the discount rate in percent. Its 19.5%

John forgot to pay his \$410.00 income tax on time. The IRS charged a penalty of 12% for the 61 days the money was late. Find the penalty that was paid. *Use a 365 day year. (\$8.22)

Mr. Grey's income rose from \$20,000 one year to \$23,000 the following year. What was the percent of increase? I (15%)

Solve for x: ax+b=cx+d (d-b/a-c)

How much money is saved by buying a shirt priced at \$80 with a 40% discount, rather than buying a shirt marked at \$90 with a discount of 35% then another 10%? (\$4.65)

Let S be the set of all integers that can be written as n2 + 1, where n is a nonzero integer. Which integers is in S?
(5,17)

A bag contains only red marbles, blue marbles, and yellow marbles. The probability of randomly selecting a red marble from the bag is 1/4, and the probability of randomly selecting a blue marble is 1/6. Which could be the total number of marbles in the bag?
(12,26)

The Athletic Club is a new facility under development. The business expects total expenses of \$142,000 in the first year. It will set the membership fee at \$500 and expects to attract 300 members in the first year. It could rent additional space for an extra \$12,000 per year. The extra space may attract more members because of the added space. Determine Vermont Athletic Club's earnings (the difference between expenses and revenues) if this extra space is rented and results in a total of 320 memberships in the first year. (6,000)

[Edited 2008-12-22 09:46:06]

ANITIX87
Posts: 2998
Joined: Mon Mar 07, 2005 4:52 am

### RE: I Need A Little Help With Math

I'll give them a shot...

 Quoting KLM672 (Reply 5):On a blueprint, 1/4 inch represents 16 feet. If a drive way is 40 feet long, what is its length, in inches, on the map? (5/8)

If 1/4 inch represents 16 feet, then you must see how many times 16 feet goes into 40. Therefore, 40/16 = 2.5. Now, multiply this by your original 1/4 inch, to get 5/8.

 Quoting KLM672 (Reply 5):A rabbit grows so that every 2 months it doubles in weight. However, the rabbit will never go over 75 lbs. If a bunny if born on July 15th weighing 2 lbs, in which month will it weight 46 lbs? (April)

You know it doubles every two months, so after 2 months it's at 4 pounds, after four months, 8 pounds, etc. Just keep doubling until you get to 46 pounds, and you find that it's in July of the next year (it's not exactly July, but the rabbit will weigh 32 pounds in March, and 64 in May, so you estimate April.

 Quoting KLM672 (Reply 5):If a person puts 1 Cent in a piggy bank on the first day, 2 cents on the second, 3 cents on the third etc, how much money will be in the bank after 50 days? (\$12.75)

Just keep adding 1+2+3+4+5+6+...+50. You get 1,275 cents, or \$12.75.

 Quoting KLM672 (Reply 5):On a map, the length of a nature-center trail is 9.7 centimeters. If the scale is 3 centimeters to 25 kilometers, what is the actual length of the trail? (80.8 Kilometers)

Same as number 1, but in the opposite direction. Divide, 9.7/3, and you get 3.2333. Then multiply by 25, and you get 80.8.

 Quoting KLM672 (Reply 5):In a sale, the prices of a computer is reduced from \$1280 to \$1030. Find the discount and the rate of discount. Round the discount rate to the nearest tenth of a percent if necessary. I got the discount which is \$250 = 1280-1030=250 but I am not sure how to do figure out the discount rate in percent. Its 19.5%

You are right in the discount, now just divide 250/1280. You get 0.1953, which you have to multiply by 100 to get the percentage, 19.53 percent.

 Quoting KLM672 (Reply 5):John forgot to pay his \$410.00 income tax on time. The IRS charged a penalty of 12% for the 61 days the money was late. Find the penalty that was paid. *Use a 365 day year. (\$8.22)

I don't know why the problem is worded this way. If the IRS charged 12 percent penalty for 61 days, then you need to find how much that is in terms of an annual percent penalty. Therefore, divide, 61/365 = 0.1671. Multiply by 12 percent to get the penalty charge for the time period given, and then multiply THAT result by 410, to get \$8.22.

 Quoting KLM672 (Reply 5):Mr. Grey's income rose from \$20,000 one year to \$23,000 the following year. What was the percent of increase? I (15%)

Same as the one for the store discount. Subtract 23,000-20,000 = 3,000. Then divide by the original income, 20,000. So, 3000/20000 = 0.15, or 15 percent.

 Quoting KLM672 (Reply 5):Solve for x: ax+b=cx+d (d-b/a-c)

Move cx to the left side, and b to the right side. You then get (ax-cx) = (d-b). Factor out the x on the left, and you get x(a-c) = (d-b). Then divide by (a-c) to get x alone, and this is your result of (d-b)/(a-c)

 Quoting KLM672 (Reply 5):How much money is saved by buying a shirt priced at \$80 with a 40% discount, rather than buying a shirt marked at \$90 with a discount of 35% then another 10%? (\$4.65)

First the shirt priced at \$80. WIth a 40 percent discount, multiply 80*0.4 = 32. The new price is 80-32 = \$48. Now the second shirt. 90 dollars with a discount of 35 percent, 90*0.35 = 31.5 dollars. Subtract this from 90 to get the new price, which is 90-31.5 = 58.5 dollars. Now take another 10 percent off of that, 58.5*0.1 = 5.85. Subtract from 58.5 and you get a new price of \$52.65. Now subtract 52.65 - 48 = 4.65, which is your total savings.

 Quoting KLM672 (Reply 5):Let S be the set of all integers that can be written as n2 + 1, where n is a nonzero integer. Which integers is in S? (5,17)

This must have been a multiple choice question, because you can put anything greater than of equal to 0 in for "n" and you'll get a positive integer for S. If it is multiple choice, I would approach it as follows: First, solve for S. Since S = n(squared) + 1, then S-1 = n(squared). Therefore, n = square root (S-1). Plug in your choices for S and see which ones yield a positive non-zero integer.

 Quoting KLM672 (Reply 5):A bag contains only red marbles, blue marbles, and yellow marbles. The probability of randomly selecting a red marble from the bag is 1/4, and the probability of randomly selecting a blue marble is 1/6. Which could be the total number of marbles in the bag? (12,26)

Again, this must be multiple choice because there is in infinite number of answers. Without the other choices, it is hard to give you a concrete approach to a question like this.

 Quoting KLM672 (Reply 5):The Athletic Club is a new facility under development. The business expects total expenses of \$142,000 in the first year. It will set the membership fee at \$500 and expects to attract 300 members in the first year. It could rent additional space for an extra \$12,000 per year. The extra space may attract more members because of the added space. Determine Vermont Athletic Club's earnings (the difference between expenses and revenues) if this extra space is rented and results in a total of 320 memberships in the first year. (6,000)

You know your total expenses are 142,000 + 12,000 = 154,000 dollars. Now, assume 320 memberships at \$500 dollars per membership, and the revenue is 320*500 = 160,000 dollars. Therefore, "profit = revenue - expenses", so profit = 160000 - 154000 = 6,000 dollars. There you go.

Hope that helped. When reviewing things like this, it's best to really try them yourself and look for other examples that are worked out (in your notes or your textbook) that are similar. Also, it's good to ask someone who you can SEE work out the problems, as it will help you visualize for your exam.

TIS
www.stellaryear.com: Canon EOS 50D, Canon EOS 5DMkII, Sigma 50mm 1.4, Canon 24-70 2.8L II, Canon 100mm 2.8L, Canon 100-4

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Joined: Mon Sep 27, 2004 11:36 pm

### RE: I Need A Little Help With Math

The best way to learn is to try it yourself, so I will try and give you some pointers that might be helpful. If you still don't fully understand, I'd be happy to help out.

 Quoting KLM672 (Reply 5):On a blueprint, 1/4 inch represents 16 feet. If a drive way is 40 feet long, what is its length, in inches, on the map? (5/8)

The Rule of Three is very helpful here

 Quoting KLM672 (Reply 5): A rabbit grows so that every 2 months it doubles in weight. However, the rabbit will never go over 75 lbs. If a bunny if born on July 15th weighing 2 lbs, in which month will it weight 46 lbs? (April)

This one is actually quite easy, just keep doubling it  .

 Quoting KLM672 (Reply 5): On a map, the length of a nature-center trail is 9.7 centimeters. If the scale is 3 centimeters to 25 kilometers, what is the actual length of the trail? (80.8 Kilometers)

Rule of Three once again.

 Quoting KLM672 (Reply 5):I got the discount which is \$250 = 1280-1030=250 but I am not sure how to do figure out the discount rate in percent. Its 19.5%

Just remember New divided by old *100%. The 'New' in this case is the thing you'd like the percentage of, the 'Old' is the thing that it is compared to.

 Quoting KLM672 (Reply 5):John forgot to pay his \$410.00 income tax on time. The IRS charged a penalty of 12% for the 61 days the money was late. Find the penalty that was paid. *Use a 365 day year. (\$8.22)

Suppose you're paying 12% on \$410, that is \$410*0.12. But you are not a full year late, you are 61/365 year late.....

 Quoting KLM672 (Reply 5): Mr. Grey's income rose from \$20,000 one year to \$23,000 the following year. What was the percent of increase? I (15%)

Once again that New/Old thingie

 Quoting KLM672 (Reply 5):Solve for x: ax+b=cx+d

This is something that you'll only learn with doing it over and over again.The one thing you have to remember is that when you move it from left to right (or oposite) of the equal sign it becames it's oposite (so plus becomes minus, minus becomes plus). The things I changed compared to the line above are underlined.

ax=cx+d-b
ax-cx=d-b

Now there are 2 x's on the left, but you want only one. Thankfully both 'parts' have an x in it so we can get that loose. The way to note this down is x(..+..) where x can be multiplied with both parts in the bracket to get the old parts again.

x(a-c)=d-b

Now you need to divide both parts by (a-c) to get the x 'alone' on the left.

x=(d-b)/(a-c)

note the use of brackets to indicate those variables belong together. Because of the way mathematics works (first multiply/divide, than add/subtract). this is something very different from the thing you wrote down. In my case, the d-b are above the line, a-c is below it. In what you wrote down you just divide b by a, and then do those things with d and c.

 Quoting KLM672 (Reply 5):How much money is saved by buying a shirt priced at \$80 with a 40% discount, rather than buying a shirt marked at \$90 with a discount of 35% then another 10%? (\$4.65)

So you need to figure out what the shirts actually cost. The first shirt costs 60% of the original price (80 times 0.6 is....?), the second one costs 65% of \$90 (90 times 0.65 is...) and then 90% of that price (.... times 0.9 is ....). The difference in cost is what you save.

 Quoting KLM672 (Reply 5): Let S be the set of all integers that can be written as n2 + 1, where n is a nonzero integer. Which integers is in S? (5,17)

must be the way it's asked, I don't get this one.....

 Quoting KLM672 (Reply 5): The Athletic Club is a new facility under development. The business expects total expenses of \$142,000 in the first year. It will set the membership fee at \$500 and expects to attract 300 members in the first year. It could rent additional space for an extra \$12,000 per year. The extra space may attract more members because of the added space. Determine Vermont Athletic Club's earnings (the difference between expenses and revenues) if this extra space is rented and results in a total of 320 memberships in the first year.

Don't let the long text distract you, just filter out the things you need. You need to know the earnings, which are the differences between expenses and revenues. So go looking for the expenses in the question (normal expenses + extra rent) and for the revenues (number of members times the membership fee).

Good luck/have fun!

ANITIX87
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Joined: Mon Mar 07, 2005 4:52 am

### RE: I Need A Little Help With Math

Also curious where you're going to school. Your age implies university, which begs the question, have you gone directly to the professor for help? University professors are often the most valuable asset in a course that is giving you trouble.

TIS
www.stellaryear.com: Canon EOS 50D, Canon EOS 5DMkII, Sigma 50mm 1.4, Canon 24-70 2.8L II, Canon 100mm 2.8L, Canon 100-4

oly720man
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Joined: Fri May 21, 2004 7:13 am

### RE: I Need A Little Help With Math

 Quoting ANITIX87 (Reply 6):Quoting KLM672 (Reply 5): If a person puts 1 Cent in a piggy bank on the first day, 2 cents on the second, 3 cents on the third etc, how much money will be in the bank after 50 days? (\$12.75) Just keep adding 1+2+3+4+5+6+...+50. You get 1,275 cents, or \$12.75.

This is the sum of a series which is 0.5*n*(n+1), here 0.5*50*51=0.5*2550 = 1275

 Quoting KLM672 (Reply 5):A bag contains only red marbles, blue marbles, and yellow marbles. The probability of randomly selecting a red marble from the bag is 1/4, and the probability of randomly selecting a blue marble is 1/6. Which could be the total number of marbles in the bag? (12,26)

Can't see how 26 can be an answer to this. Any multiple of 12 I'd have thought. Sum of probabilities must be 1 so the probability for yellow must be 7/12.

 Quoting KLM672 (Reply 5):Let S be the set of all integers that can be written as n2 + 1, where n is a nonzero integer. Which integers is in S? (5,17)

I assume this is n^2+1. Was there a choice?
wheat and dairy can screw up your brain

ag92
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### RE: I Need A Little Help With Math

Dude, are these the problems?
Is your age really 21-25 because these are the sort of questions we did in Grade 5-8

 Quoting KLM672 (Reply 5):On a blueprint, 1/4 inch represents 16 feet. If a drive way is 40 feet long, what is its length, in inches, on the map?

The english was slightly confusing here but after having a look at the answer it made complete sense. Mathematically the simple thing is find a factor of 16feet and 40feet which could be 8, 4, 2, or 1 feet. I will use 8 feet, and if 1/4inch represents 16feet then 1/8inch will represent 8 feet (1/4)/(2). If 1/8 inch represents 8 feet then we need to multiply each figure by five just as it is done in ratios sort of thing, and you will find 8feet x 5 = 40feet and 1/8inch x 5 = 5/8inch

 Quoting KLM672 (Reply 5):A rabbit grows so that every 2 months it doubles in weight. However, the rabbit will never go over 75 lbs. If a bunny if born on July 15th weighing 2 lbs, in which month will it weight 46 lbs? (April)

This question I found the hardest but none the less rather easy.
This is actually extremley easy to be done by just counting out the powers of 2, however mathematically log246=x . Just keep in mind that its every two months not one month, and as the answer will be a decimal value between 32 and 64, you know 2^5 is 32 and 2^6=64, so when x=6 that means 12 month but 2^5 = 10months, however the weight started at 2, so it becomes between 10months and 8months

 Quoting KLM672 (Reply 5):If a person puts 1 Cent in a piggy bank on the first day, 2 cents on the second, 3 cents on the third etc, how much money will be in the bank after 50 days? (\$12.75)

Mathematically its using the sign of "the sum of" x with the upper limit 50 and the lower limit 1, kind of hard to explain online, however in this sort of equasion I would just sum up the numbers, 1+49=50, 2+48=50, and we know there are 24 pairs like that because remember there is only 1 25, so it becomes 12.00 + the leftover 75 cents gives it 12.75

 Quoting KLM672 (Reply 5): On a map, the length of a nature-center trail is 9.7 centimeters. If the scale is 3 centimeters to 25 kilometers, what is the actual length of the trail? (80.8 Kilometers)

look at the first question, very similar technique

 Quoting KLM672 (Reply 5): In a sale, the prices of a computer is reduced from \$1280 to \$1030. Find the discount and the rate of discount. Round the discount rate to the nearest tenth of a percent if necessary. I got the discount which is \$250 = 1280-1030=250 but I am not sure how to do figure out the discount rate in percent. Its 19.5%

Well done, you found the discount rate, simple mathematics, the percentage rate is (original rate - discounted rate)/(original rate) x 100%

 Quoting KLM672 (Reply 5):John forgot to pay his \$410.00 income tax on time. The IRS charged a penalty of 12% for the 61 days the money was late. Find the penalty that was paid. *Use a 365 day year. (\$8.22)

I think this question has to many variables,
1) How long did he not pay for? 61 days? or 365 days?
2) If the latter what was the rate after the 61 days?
Ok nvm, I found how the answer was found, basically the interest is charged 12% per year, so if its only for 61 days, it will be 61/365 x (12/100 - this is the percentage) x 410 the initial amount

 Quoting KLM672 (Reply 5): Mr. Grey's income rose from \$20,000 one year to \$23,000 the following year. What was the percent of increase? I (15%)

(New value - old value)/old value x 100% - similar to a previous question however this was an INCREASE not a DECREASE

 Quoting KLM672 (Reply 5): Solve for x: ax+b=cx+d (d-b/a-c)

ax+b=cx+d
ax+b-cx-d=0
x(a-c)+b-d=0
x(a-c)=(d-b)
x=(d-b)/(a-c)

The answer given above is WRONG!

 Quoting KLM672 (Reply 5): How much money is saved by buying a shirt priced at \$80 with a 40% discount, rather than buying a shirt marked at \$90 with a discount of 35% then another 10%? (\$4.65)

80x((100-40)/100) = 80-32 which gives 48 dollars
90x0.65 (see above calc) = 27+4.5 = 31.5, 90-31.5 = 58.5dollars
58.5 x 0.9 = 58.5-5.85 = 52.65

52.65-48=4.65

If you can get this technique right then next time just realize that the second value is 65x0.9 = 65-6.5 = 58.5% of the ORIGINAL PRICE so its a 41.5% DISCOUNT

 Quoting KLM672 (Reply 5): Let S be the set of all integers that can be written as n2 + 1, where n is a nonzero integer. Which integers is in S? (5,17)

wow, any number which fits the equation becasue n can be any value greater then zero. There is some part of the question missing for sure

 Quoting KLM672 (Reply 5): A bag contains only red marbles, blue marbles, and yellow marbles. The probability of randomly selecting a red marble from the bag is 1/4, and the probability of randomly selecting a blue marble is 1/6. Which could be the total number of marbles in the bag? (12,26)

Missing some vital information

 Quoting KLM672 (Reply 5):The Athletic Club is a new facility under development. The business expects total expenses of \$142,000 in the first year. It will set the membership fee at \$500 and expects to attract 300 members in the first year. It could rent additional space for an extra \$12,000 per year. The extra space may attract more members because of the added space. Determine Vermont Athletic Club's earnings (the difference between expenses and revenues) if this extra space is rented and results in a total of 320 memberships in the first year. (6,000)

320x500=160000
160000-154000=6000

---------------------------------

Now let me be absolutely honest, and if feelings are hurt then I apologize BUT this is too simple maths, I mean you are not 21-25 if so, then I'm sorry how did you not only pass your maths but also any other exam related to maths such as Physics ever in your life. These are the sort of stuff 12-14 year olds do and the last one is literally ab -cd sort of question where abcd are given right in front of you with no calculations. I only did this because I am going to undertake my sats soon and the one thing I don't want to get wrong is maths, I aim for a perfect in that because I know its not gonna be that hard but really this is simpler then the simplest middle school questions. I say you may not even be 13 year old

klm672
Topic Author
Posts: 2563
Joined: Mon Oct 04, 1999 6:09 am

### RE: I Need A Little Help With Math

Thanks for all the very quick replies! Yes it was n^2+1. No, teacher for this, I've been out of math classes for a while, this is the final "test" that every student must get at least a 75 on before you can graduate. Its a general college thing, no class.

 Quoting Ag92 (Reply 10):Now let me be absolutely honest, and if feelings are hurt then I apologize BUT this is too simple maths, I mean you are not 21-25 if so, then I'm sorry how did you not only pass your maths but also any other exam related to maths such as Physics ever in your life. These are the sort of stuff 12-14 year olds do and the last one is literally ab -cd sort of question where abcd are given right in front of you with no calculations. I only did this because I am going to undertake my sats soon and the one thing I don't want to get wrong is maths, I aim for a perfect in that because I know its not gonna be that hard but really this is simpler then the simplest middle school questions. I say you may not even be 13 year old

...And thats why I didn't want to post them here. I am glad that I didn't get any more of these or at least everyone kept it to themselves. Yes, I'm 22 years old and its is for college. I suck at math, I know these are "basic" but its just not something I do everyday and I haven't had to deal with any math (in the classroom) in a few years. I only took one math class in college and I got a C-. I used all my resorces including friends, tutoring and the professior. I have one more class to do and I'll probably be do the same. Sorry for ruining your day.

klm672
Topic Author
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### RE: I Need A Little Help With Math

 Quoting ANITIX87 (Reply 6):Quoting KLM672 (Reply 5): If a person puts 1 Cent in a piggy bank on the first day, 2 cents on the second, 3 cents on the third etc, how much money will be in the bank after 50 days? (\$12.75) Just keep adding 1+2+3+4+5+6+...+50. You get 1,275 cents, or \$12.75.

Isnt there a faster trick to that...? I am trying to recall how we did it but its not coming to me.

oly720man
Posts: 5813
Joined: Fri May 21, 2004 7:13 am

### RE: I Need A Little Help With Math

 Quoting KLM672 (Reply 12):Isnt there a faster trick to that...? I am trying to recall how we did it but its not coming to me.

 Quoting Oly720man (Reply 9):This is the sum of a series which is 0.5*n*(n+1), here 0.5*50*51=0.5*2550 = 1275

wheat and dairy can screw up your brain

Posts: 3957
Joined: Mon Sep 27, 2004 11:36 pm

### RE: I Need A Little Help With Math

 Quoting Oly720man (Reply 9): This is the sum of a series which is 0.5*n*(n+1), here 0.5*50*51=0.5*2550 = 1275

I believe you it's true, however I fail to see why that formula is the way it is, would you care to explain? Not to second guess you, I just hate to not understand it  .

MCOflyer
Posts: 7088
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### RE: I Need A Little Help With Math

KLM,

Is this the math exit exam for community college? If so, than per my college; you need a combined average B of the two classes.

Hunter
Never be afraid to stand up for who you are.

klm672
Topic Author
Posts: 2563
Joined: Mon Oct 04, 1999 6:09 am

### RE: I Need A Little Help With Math

Hunter,

Yeah, kinda. Its kinda more relaxed I guess. Here you need a 75% or higher. 20 questions and they offer it a few times a month. I have til May to pass  .

dtwclipper
Posts: 6668
Joined: Wed Oct 29, 2003 3:17 am

### RE: I Need A Little Help With Math

Not to be a pest here but you posted this in '04

What's going on here?
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klm672
Topic Author
Posts: 2563
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### RE: I Need A Little Help With Math

DTW- That was a different math, nothing crazy going on, just bad at math, still.

MCOflyer
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### RE: I Need A Little Help With Math

KLM, do not feel bad. I received a "C" in intermediate algebra.

Hunter
Never be afraid to stand up for who you are.

GAIsweetGAI
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### RE: I Need A Little Help With Math

 Quoting JRadier (Reply 14):I believe you it's true, however I fail to see why that formula is the way it is, would you care to explain? Not to second guess you, I just hate to not understand it Silly.

True for n=0: 0*(0+1)/2=0.

Suppose the formula is true for an integer n, and try it for n+1:

1+2+...+n+1=n*(n+1)/2+n+1
which equals (n+1)*(n+2)/2 (trivial   )
"There is an art, or rather a knack to flying. The knack lies in learning how to throw yourself at the ground and miss."

airportugal310
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### RE: I Need A Little Help With Math

 Quoting KLM672 (Reply 19):DTW- That was a different math, nothing crazy going on, just bad at math, still.

im with you....math blows

simple everyday stuff i can do to make sure bills are paid etc blah blah blah but seriously...

who gives a shit about pulling a red marble out of a bag unless you do that for a living?

answer: no one (displayed mathmatically as 0 or 1-0 = x , where x = 0)
“They bought their tickets, they knew what they were getting into. I say, let 'em crash.”

HB-IWC
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Joined: Fri Sep 22, 2000 1:09 am

### RE: I Need A Little Help With Math

 Quoting JRadier (Reply 14):I believe you it's true, however I fail to see why that formula is the way it is, would you care to explain?

The formula stated by the previous poster is a special case of the sum formula for terms in an arithmetic sequence. The general formula for the sum Sn of the first n terms of an arithmetic sequence is

Sn = n * [(a1 + an)/2]

where a1 is the first term and an is the n-th term of the arithmetic sequence for which the general term is described as

an = a1 + (n-1)*d

with d the common difference.

As said, the formula stated by the previous poster is a special case of this general rule that allows for the calculation of the sum of the first n integers. In this case we would choose

a1 = 1
d = 1

and hence

an = n

and therefore the sum Sn, which will now represent the sum of the first n integers will become

Sn = n * [(1 + n)/2] = 0.5 * n * (n+1)

Mir
Posts: 19491
Joined: Mon Jan 05, 2004 3:55 am

### RE: I Need A Little Help With Math

 Quoting KLM672 (Reply 5):Let S be the set of all integers that can be written as n2 + 1, where n is a nonzero integer. Which integers is in S? (5,17)

This seems like it has to be a multiple choice, since 2, 10, 26, 37, 50, etc. are also valid answers.

-Mir
7 billion, one nation, imagination...it's a beautiful day

BN747
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### RE: I Need A Little Help With Math

The best Math website on the planet...

http://www.algebrahelp.com/

BN747
"Home of the Brave, made by the Slaves..Land of the Free, if you look like me.." T. Jefferson

klm672
Topic Author
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### RE: I Need A Little Help With Math

 Quoting Mir (Reply 23):Quoting KLM672 (Reply 5): Let S be the set of all integers that can be written as n2 + 1, where n is a nonzero integer. Which integers is in S? (5,17)

 Quoting Mir (Reply 23):This seems like it has to be a multiple choice, since 2, 10, 26, 37, 50, etc. are also valid answers. -Mir

Yes, 1,5,17,28, and 36

 Quoting JRadier (Reply 14):This is the sum of a series which is 0.5*n*(n+1), here 0.5*50*51=0.5*2550 = 1275

If the problem was 30 would it then be 0.5*30*31=465 ?

ag92
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### RE: I Need A Little Help With Math

Yup thats true, I think if you want to, you could probably google it for the proof, if you want it give me a pm, and I can redo the proof for you then

MOBflyer
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### RE: I Need A Little Help With Math

What was that about?

klm672
Topic Author
Posts: 2563
Joined: Mon Oct 04, 1999 6:09 am

### RE: I Need A Little Help With Math

 Quoting ANITIX87 (Reply 6):Quoting KLM672 (Reply 5): On a blueprint, 1/4 inch represents 16 feet. If a drive way is 40 feet long, what is its length, in inches, on the map? (5/8)

 Quoting ANITIX87 (Reply 6):If 1/4 inch represents 16 feet, then you must see how many times 16 feet goes into 40. Therefore, 40/16 = 2.5. Now, multiply this by your original 1/4 inch, to get 5/8.

Sorry for the delay in responding (holidays and all). On a calculator, how do I multiply 1/4*2.5? or any other trick (non calculator),

 Quoting KLM672 (Reply 3):A bag contains only red marbles, blue marbles, and yellow marbles. The probability of randomly selecting a red marble from the bag is 1/4, and the probability of randomly selecting a blue marble is 1/6. Which could be the total number of marbles in the bag? (12,26)

 Quoting ANITIX87 (Reply 6):Again, this must be multiple choice because there is in infinite number of answers. Without the other choices, it is hard to give you a concrete approach to a question like this.

Yes, the choices are: 10, 12, 18,28,36

Also,
How do I find the rate of change? I am given a graph. Y is value of cars in thousands of dollars 5, 10, 15, 20, 25, 30. For X its number of years in use 1,2,3,4,5,6. I need to find the "rate of change". The line starts at 25 and goes down to 5. The answer is -\$3,000 per yr.

Thanks again for all the help.

Mir
Posts: 19491
Joined: Mon Jan 05, 2004 3:55 am

### RE: I Need A Little Help With Math

 Quoting KLM672 (Reply 28):On a calculator, how do I multiply 1/4*2.5?

Two ways.

1) Change 1/4 to a decimal, and then multiply it. You'll end up with .25*2.5.

2) Use the parentheses keys to put 1/4 in parentheses, then multiply it. You'll end up with (1/4)*2.5.

 Quoting KLM672 (Reply 28):How do I find the rate of change? I am given a graph.

The change in the Y axis divided by the change in the X axis. Let's say you have a graph on which the Y axis represents the value of the car and the X axis represents time. You have two points, one at (0,12) and one at (5,9). The first one represents the car's value as \$12,000 when you buy it (since time is 0) and the second represents its value five years down the road, where the car has devalued to \$9,000. To find out how much it loses per year, divide the change in Y by the change in X. The Y goes from 12 to 9. 12-9=3. The X goes from 0 to 5. 0-5=-5. Therefore, your answer will be 3/-5, or -0.6. That's how much the car's value will change per year (-\$600).

This (change in Y divided by change in X) is also called the slope of the line (the m in the y=mx+b notation).

-Mir
7 billion, one nation, imagination...it's a beautiful day

andz
Posts: 7733
Joined: Mon Feb 16, 2004 7:49 pm

### RE: I Need A Little Help With Math

 Quoting MOBflyer (Reply 27):What was that about?

After Monday and Tuesday even the calendar says WTF...

klm672
Topic Author
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Joined: Mon Oct 04, 1999 6:09 am

### RE: I Need A Little Help With Math

 Quoting Mir (Reply 29):Two ways. 1) Change 1/4 to a decimal, and then multiply it. You'll end up with .25*2.5.

Yeah, I tried that and I get 0.625. How do I then transfer that to 5/8?

Goldenshield
Posts: 5022
Joined: Sun Jan 14, 2001 3:45 pm

### RE: I Need A Little Help With Math

 Quoting KLM672 (Reply 31):Yeah, I tried that and I get 0.625. How do I then transfer that to 5/8?

Generally, you can't convert back to fractions unless you know the common denominator. I took drafting in school, and wealways used a conversion table to help us with our calculations, as we always wrote the distances in fractions on the drawing.

Here's a good conversion chart:

http://www.seoconsultants.com/charts/inches-decimal/
Two all beef patties, special sauce, lettuce, cheese, pickles, onions on a sesame seed bun.

klm672
Topic Author
Posts: 2563
Joined: Mon Oct 04, 1999 6:09 am

### RE: I Need A Little Help With Math

Thanks,
then my question is, when I am faced with a similar problem, how will I know what the correct answer is. Its multiple choice not fill in the blank.

Mir
Posts: 19491
Joined: Mon Jan 05, 2004 3:55 am

### RE: I Need A Little Help With Math

 Quoting KLM672 (Reply 31):Yeah, I tried that and I get 0.625. How do I then transfer that to 5/8?

.625 is the same as 625/1000. Reduce that, and you'll get 5/8.

-Mir
7 billion, one nation, imagination...it's a beautiful day

klm672
Topic Author
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Joined: Mon Oct 04, 1999 6:09 am

### RE: I Need A Little Help With Math

Mir,
Sorry, I guess I don't see it. When I do that (625/1000) I get 1.6....

Goldenshield
Posts: 5022
Joined: Sun Jan 14, 2001 3:45 pm

### RE: I Need A Little Help With Math

 Quoting KLM672 (Reply 35):Sorry, I guess I don't see it. When I do that (625/1000) I get 1.6....

You are reversing the order of the computation.

Instead of 625 / 1000, you did 1000 / 625.

Basically, you need to reduce to the easiest common denominator. Since 625 is a nice, round 5, we'll use that.

625 / 5 = 125, therefore 625 / 125 = 5

Then, using the same divisor with the denominator, 1000 / 125, we get 8.

Therefore, the reduction is 5 / 8.
Two all beef patties, special sauce, lettuce, cheese, pickles, onions on a sesame seed bun.

klm672
Topic Author
Posts: 2563
Joined: Mon Oct 04, 1999 6:09 am

### RE: I Need A Little Help With Math

 Quoting Mir (Reply 29):The change in the Y axis divided by the change in the X axis. Let's say you have a graph on which the Y axis represents the value of the car and the X axis represents time. You have two points, one at (0,12) and one at (5,9). The first one represents the car's value as \$12,000 when you buy it (since time is 0) and the second represents its value five years down the road, where the car has devalued to \$9,000. To find out how much it loses per year, divide the change in Y by the change in X. The Y goes from 12 to 9. 12-9=3. The X goes from 0 to 5. 0-5=-5. Therefore, your answer will be 3/-5, or -0.6. That's how much the car's value will change per year (-\$600). This (change in Y divided by change in X) is also called the slope of the line (the m in the y=mx+b notation). -Mir

According to this its -\$3,000 not -600.

oly720man
Posts: 5813
Joined: Fri May 21, 2004 7:13 am

### RE: I Need A Little Help With Math

 Quoting KLM672 (Reply 37):According to this its -\$3,000 not -600.

Mir is using different example numbers.

For your case, every year the value drops by \$5000 so I can't see where the -\$3000 comes from.

Do you have points on the graph or is it just a line that goes through \$25k after 1 year and through \$5k after 5 years?
wheat and dairy can screw up your brain

ANITIX87
Posts: 2998
Joined: Mon Mar 07, 2005 4:52 am

### RE: I Need A Little Help With Math

 Quoting Goldenshield (Reply 36):You are reversing the order of the computation. Instead of 625 / 1000, you did 1000 / 625. Basically, you need to reduce to the easiest common denominator. Since 625 is a nice, round 5, we'll use that. 625 / 5 = 125, therefore 625 / 125 = 5 Then, using the same divisor with the denominator, 1000 / 125, we get 8. Therefore, the reduction is 5 / 8.

You may be confusing him. KLM762, just take all your choices and divide them. The one that comes out to your answer (0.625) will be the correct. Just be careful not to switch the operations like you did in post 35. It's the TOP number divided by the BOTTOM number. So, for example, 5/8 is equal to 5 divided by 8, which is 0.625.

TIS
www.stellaryear.com: Canon EOS 50D, Canon EOS 5DMkII, Sigma 50mm 1.4, Canon 24-70 2.8L II, Canon 100mm 2.8L, Canon 100-4

klm672
Topic Author
Posts: 2563
Joined: Mon Oct 04, 1999 6:09 am

### RE: I Need A Little Help With Math

 Quoting ANITIX87 (Reply 39):You may be confusing him. KLM762, just take all your choices and divide them. The one that comes out to your answer (0.625) will be the correct. Just be careful not to switch the operations like you did in post 35. It's the TOP number divided by the BOTTOM number. So, for example, 5/8 is equal to 5 divided by 8, which is 0.625.

Thats much easier, thanks.

Yes, let me try and post the graph on here in a few hours when I have more time. I test is Thursday and I'm getting a little nervous. I left out a few problems because of the graphs but if I am able to post the pictures on here it could help. Another problem is I am given an equation and I need to find the graph that matches it.

RIHNOSAUR
Posts: 336
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### RE: I Need A Little Help With Math

 Quoting ANITIX87 (Reply 39):Just be careful not to switch the operations like you did in post 35. It's the TOP number divided by the BOTTOM number. So, for example, 5/8 is equal to 5 divided by 8, which is 0.625.

Seems like every one here has done a excellent job in helping out....just for what ever its worth and to re-stress TIS point, in general when doing math remember the following:

division ( / ) and subtraction ( - ) are NON commutative i.e. its a fancy way of saying that it makes a difference in the order you make the operation.

On the other hand addition (+) and multiplication ( x or * ) are commutative i.e. it does NOT matter in which order you perform the operation.

so when using your calculator, keep in mind what type of operation you are about to enter from your paper into the calculator. Therefore depending on the operators you see, you need to ensure you "input" what you want. Other wise you will get an answer that is wrong but you actually have been doing the wrong operation the hole time.

along the same lines..make sure to respect parenthesis and treat them from "inside out"
e.g.

( (5y - 34g) * (e + f) + 1/ (a+b) ) * (1/2)

in order to evaluate the above equation for whatever values you want to assign to each letter, you must first "evaluate" each parenthesis individually and then perform the operations that apply to the groups in the parenthesis... same commutation (and non-commutation) rules described above apply.

Sorry if it seems off topic..but from reading the posts I think some of these concepts will become very useful.

cheers
particles and waves are the same thing, but who knows what that thing is...

oly720man
Posts: 5813
Joined: Fri May 21, 2004 7:13 am

### RE: I Need A Little Help With Math

 Quoting KLM672 (Reply 40):Another problem is I am given an equation and I need to find the graph that matches it.

What sort of equation?

If it's of the y = mx+c variety then it's a straight line.

But with any equation, there are a number of things you can do to work out what the graph looks like.

1) find y when x = 0 and find x when y = 0

So when x = 0 you find where the line crosses the y axis and when y = 0 you find when the line crosses the x axis

2) find the gradient =y/x

if it's positive the line goes from "south west" to "north east", if it's negative it goes from "north west" to "south east"

for an equation of the y=mx+c variety it's the value of m that matters.

3) find y when x is large, find x when y is large (though this is more applicable to quadratic equations and more complicated ones)
wheat and dairy can screw up your brain

klm672
Topic Author
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### RE: I Need A Little Help With Math

Seems like dial up won't let me post the pictues. Anyways, I am given a bunch of different graphs and it says to match them

y=1/2x+1
y=2x+1
y=-1/2x+1
y=2x+1

In the rectangles below (ok, so they arent here) the ratio of length to width is the same. Find the length of the larger rectangle.

the smaller one is 20ft ("side")x30ft("top"). The bigger one is just 50ft on the "side".
The anwser is 75ft

Confuscius
Posts: 3711
Joined: Wed Aug 29, 2001 12:29 am

### RE: I Need A Little Help With Math

I can help as long as it's only addition and subtraction...and only whole numbers.
Ain't I a stinker?

oly720man
Posts: 5813
Joined: Fri May 21, 2004 7:13 am

### RE: I Need A Little Help With Math

 Quoting KLM672 (Reply 43):y=1/2x+1 y=2x+1 y=-1/2x+1 y=2x+1

Using what I said;

For y=1/2x+1

when x = 0, y = 1----> y = 1/2*0+1 = 1
when y = 0, 0.5x+1=0 so x = -2

y/x = 1/2, so positive, line goes from bottom left to top right and the gradient is 1/2 so shallow

Find the graph where the line crosses the x axis at -2 and the y axis at +1.

Same idea for the other equations.

 Quoting KLM672 (Reply 43):In the rectangles below (ok, so they arent here) the ratio of length to width is the same. Find the length of the larger rectangle. the smaller one is 20ft ("side")x30ft("top"). The bigger one is just 50ft on the "side". The anwser is 75ft

The ratio is constant = 30/20 = 1.5

On the second rectangle the 50 is equivalent to the 20 on the first rectangle so the 30 is equivalent to the unknown length

Because the ratio of sides is 1.5 the unknown value is 1.5 x 50 = 75.

Another way to look it is to say that the ratio of rectangles is 50/20 = 2.5 so the new side is 2.5 x 30 = 75.
wheat and dairy can screw up your brain

klm672
Topic Author
Posts: 2563
Joined: Mon Oct 04, 1999 6:09 am

### RE: I Need A Little Help With Math

 Quoting Mir (Reply 29):The change in the Y axis divided by the change in the X axis. Let's say you have a graph on which the Y axis represents the value of the car and the X axis represents time. You have two points, one at (0,12) and one at (5,9). The first one represents the car's value as \$12,000 when you buy it (since time is 0) and the second represents its value five years down the road, where the car has devalued to \$9,000. To find out how much it loses per year, divide the change in Y by the change in X. The Y goes from 12 to 9. 12-9=3. The X goes from 0 to 5. 0-5=-5. Therefore, your answer will be 3/-5, or -0.6. That's how much the car's value will change per year (-\$600). This (change in Y divided by change in X) is also called the slope of the line (the m in the y=mx+b notation).

Nice! I plugged my numbers in and it worked perfect, thanks.

klm672
Topic Author
Posts: 2563
Joined: Mon Oct 04, 1999 6:09 am

### RE: I Need A Little Help With Math

 Quoting KLM672 (Reply 25):Quoting Mir (Reply 23): Quoting KLM672 (Reply 5): Let S be the set of all integers that can be written as n2 + 1, where n is a nonzero integer. Which integers is in S? (5,17) Quoting Mir (Reply 23): This seems like it has to be a multiple choice, since 2, 10, 26, 37, 50, etc. are also valid answers. -Mir Yes, 1,5,17,28, and 36

What exactly do I need to find here. Why is 5,17 ok and 17,28 and 36 not.

oly720man
Posts: 5813
Joined: Fri May 21, 2004 7:13 am

### RE: I Need A Little Help With Math

 Quoting KLM672 (Reply 47):Why is 5,17 ok and 17,28 and 36 not.

5 = 2^2+1
17 = 4^2+1

28 = 5^2+ ___3___ --> doesn't fit equation n^2+1
36 = 6^2+ ___0___ --> doesn't fit equation n^2+1
wheat and dairy can screw up your brain

klm672
Topic Author
Posts: 2563
Joined: Mon Oct 04, 1999 6:09 am

### RE: I Need A Little Help With Math

Hey.
Is anyone willing to make up a few problems similar to what I have posted as a little practice for me (Please make them multiple choice). The test is Thursday so the sooner the better. Please send them to [email protected] I'd really appreciate that.

Thanks
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