You already know a fraction is equal parts of a whole. But the "whole" doesn't have to be one pizza — it can be a quantity, like 12 sweets or 20 pounds. Finding a fraction of an amount just means splitting that amount into equal parts and keeping some of them.

Take \frac{1}{4} of 12. The bottom number, the denominator, says split into four equal groups — and splitting into equal groups is exactly division:

So \frac{1}{4} of 12 is 3 — one of the four equal groups.

To find \frac{3}{4} of 12, do the same split, then keep three of the groups. The top number, the numerator, tells you how many groups to take, so you multiply:

That is the whole rule in one line: divide by the bottom, times by the top. Divide by the denominator to find one group, then multiply by the numerator to take that many groups.

See it built

Watch a set of objects get shared into the denominator's number of equal groups, then the numerator's number of groups taken. Counting the taken objects gives the answer. Step through it.

See it explained

Sal Khan works through finding a fraction of a whole number using two approaches.