Work out percentages, percentage change, and reverse percentages such as removing tax from a total.
Four calculations in one place: what is X percent of Y, X is what percent of Y, the percentage change from one value to another, and the original value before a percentage was applied.
That last one is the reverse percentage people usually get wrong. Removing 20 percent tax from a total means dividing by 1.2, not subtracting 20 percent.
What is the difference between percentage change and percentage points? Moving from 5 percent to 10 percent is a rise of 5 percentage points, but a 100 percent increase. Both are correct and they describe different things.