25% off a $40 jacket
A jacket costs forty dollars and is twenty-five percent off. How much money do you save?
Twenty-five percent means twenty-five out of every hundred — the same as one out of four equal parts.
We can set up a proportion: part over whole equals percent over one hundred.
The whole is the original price — forty dollars.
The percent is twenty-five out of one hundred.
The part is what we want to find. Let's call it x.
Now cross-multiply: one hundred times x equals twenty-five times forty.
Twenty-five times forty is one thousand.
Divide both sides by one hundred. x equals ten.
You save ten dollars! The sale price is just thirty dollars.