The three percent questions
A part, a whole and a percent are tied together. Given any two of them, how do you find the third?
Where you are 3 inside
What this area is about
Every percent statement links three numbers: a whole, a part of it, and the percent the part is of the whole. “207 is 45\% of 460” has all three. A real question hides one of them, and which one is hidden decides the move. Finding the part, a percent of a number, is the familiar case; this area handles the other two, and one equation that covers all three.
How these fit together
The two missing-number moves. Finding what percent one number is of another divides the part by the whole and reads the result as hundredths. Finding the whole from a part and a percent runs backwards: it scales the part up to the amount that goes with 100\%.
One equation for all three. Solving percent problems with an equation or a proportion writes part \displaystyle = \frac{p}{100} \times whole, or the proportion \displaystyle \frac{\text{part}}{\text{whole}} = \frac{p}{100}, and solves for whichever number is missing.
A path through it
No child here requires another, so the three can be taken in any order. Finding the whole and the percent equation both assume solving a proportion; finding the percent assumes only changing a fraction to a percent.
Finish here and you can run a percent change backwards and work out markup and margin.