Proportions

Definition: 2 equal ratios.

Example 1:

2/4 = 8/16

-OR-

2:4 = 8:16

Cross products should always be equal. So in this example:
2 * 16 = 32 (extremes)
4 * 8 = 32 (means)

What if 16 was missing how would you find it?

2/4 = 8/?

Solve:

First multiple the cross products:
2 * x = 4 * 8
Then divide
2/2 = x
32/2 = 16