## Labels

- 2D spatial reasoning
- 3D spatial reasoning
- algebra
- alternate number bases
- area problems
- consecutive numbers and other sequences
- counting problems
- factors and multiples
- finding and extending patterns
- fractions
- geometry
- graph theory
- logic
- nets
- number bond practice for young children
- place value
- practice with addition/subtraction
- practice with decimal arithmetic
- practice with multiplication
- reflections/rotations

## Wednesday, November 24, 2021

### The Stripey Triangle Problem

## Tuesday, November 9, 2021

### The Consecutive Number Problem

Ginger writes down a sequence of numbers. Each is a positive whole number from 1 to 11, and she uses each number only once. Henrietta looks at the sequence and notices that for every pair of numbers next to each other in the sequence, one is divisible by the other. What is the maximum number of numbers that Ginger wrote down?

For the solution, click "Read More" below.

## Sunday, November 7, 2021

### The Rolling Cube Problem

For the solution, click "Read More" below.

## Monday, October 25, 2021

### The Birthday Party Problem

Betty’s friends threw her a birthday party. Everyone (including Betty) met exactly 3 new people at the party.

When Betty told her mom about the party later, her mom said, “That sounds like fun! How many people were there at the party?”

“I think there were 14, or maybe 15, including me,” answered Betty.

Question: If Betty was right that there were either 14 or 15 people at the party, then which number is correct?

For the solution, click "Read More" below.

## Saturday, October 23, 2021

### The Isosceles Triangle Problem

The lines below are parallel.

For the solution, click "Read More" below.

## Friday, September 24, 2021

### Four fours!

Place operation symbols between the ones to make the equations true. (Use the four operations and parentheses.)

1 1 1 1 = 0

1 1 1 1 = 1

1 1 1 1 = 2

1 1 1 1 = 3

1 1 1 1 = 4

Work out:

4 4 4 4 = 0

4 4 4 4 = 1

4 4 4 4 = 2

4 4 4 4 = 3

4 4 4 4 = 4

4 4 4 4 = 5

4 4 4 4 = 6

4 4 4 4 = 7

4 4 4 4 = 8

4 4 4 4 = 9

4 4 4 4 = 10

For the solution, click "Read More" below.

## Thursday, March 25, 2021

### Toothpick Puzzle!

This is a repost of a problem from several years ago. This time I am including an interactive document that you can use to move your toothpicks around and create your figures. First, make sure you are signed in with a Google/gmail account - otherwise you will be able to see the document but can't make your own copy. Open the document and then under the "file" menu, click "make a copy" to make your own copy: Toothpick Perimeter document

Here's the problem:

Notice that you can make figures with toothpicks. We can think of each toothpick as a unit of length. Below I made a figure with a perimeter of 12 and an area of 9:

__: How many different__

**Question***areas*can be made with the same perimeter of 12? (Notice that we can make a perimeter of 8 simply by "bending in" a corner of the figure. The area is smaller but the perimeter is the same.) What is the smallest area you can make with 12 toothpicks? The largest? Can you make every whole number in between?

__The Moscow Puzzles__.)

For the solution, click "Read More" below.