Here's the game:
 

We want to write fractions using
the smallest numbers possible.

For example, look at 100/200

Can you think of a better way to write this using smaller numbers? Let's see...

What if we divided the numerator and denominator by 100?

(100/100)/(200/100) = 1/2

Oh, yeah... This is a lot better!

Here are the two rules:

1) You can divide the numerator and the denominator by any number... as long as you use the same number for both! 
For example, you can't divide the numerator by 3 and the denominator by 5.
2) You need to get the numerator and denominator as small as possible.