Crazy Paper Things

Apparently there are lots of different “crazy paper things” floating around on YouTube. I have yet to make any so I’m not sure if they actually work or not but they do look awesome!

I’m sure there are more but these will definitely get you started.


Wait, What?

Sometimes math can be used for trickery. There are card tricks that utilize math in order to amaze others. Then there are just some calculations that appear to hold true but really “hide” a small truth from people who may not see it.


a = x

(add a to both sides)

a + a = a + x

(combine like terms)

2a = a + x

(subtract 2x from both sides)

2a – 2x = a + x – 2x

(combine like terms)

2a – 2x = a – x

(factor out a 2)

2 (a – x) = a – x

(divide both sides by a – x)

2 = 1

Hmmm… That doesn’t make sense. There’s a mathematical fact that isn’t explicit here but with knowledge of it, you won’t be fooled by the conclusion here that 2 equals 1. Do you know what it is?

While you’re working on that, check out for some math-related funnies.

Get Them All Across the River

Below is a somewhat popular logic puzzle that I presented to my class to change the routine up a bit. I was able to utilize an interactive whiteboard with this so that the animals and cabbage could be dragged around to check solution methods. After immediately pointing out that the cabbage was not proportional, they really got into it and were able to solve it quite quickly.

Here’s the Dilbert comic that reminded me of this challenge:

The Eyeballing Game

I came across this site a while ago and only now remembered it. It can be pretty addicting, both for mathy and non-mathy people alike. Enjoy!

Test your geometry skills by trying to eyeball a parallelogram,


angle bisector,

the center of a triangle,

the center of a circle,

a right angle,

and where three lines converge.

The Eyeballing Game

More Math “Magic”

Take any three-digit number and write it down twice to make a six-digit number.

(For example, the three-digit number 123 would be the six-digit number 123,123).

No matter what three-digit number you choose to start with, your six-digit number will be divisible by 7, 11, and 13.

Fancy stuff.


from xkcd

Sudoku. The Rules: You must fill in each box with a number between 1 and 9 (usually), but no number can appear more than once in each 3×3 square, row, or column. You will use all the numbers 1-9 in each 3×3 square, row, and column to fill up the entire Sudoku grid.

My favorite website to use is Web Sudoku. They have levels ranging from Easy to Evil, and they tell you if you’re on the right track or if you have an error. If you are a complete nerd like I am, you can ignore that feature by making sure to play without hitting the enter key after putting in the numbers.