Fractions of a Set

Fractions of a Set

When you find a fraction of a set, you are taking part of a group of equal items. The key idea is to first find the total number of items, then divide that total into equal parts, and finally take the number of parts named by the fraction.

Method

1. Find the denominator: this tells you how many equal parts the set is split into.
2. Divide the set by the denominator.
3. Use the numerator: take that many of the equal parts.
4. Count the items in the chosen parts.

Example idea

If you need frac{3}{4} of a set of 12, split 12 into 4 equal groups. Each group has 3 items, so 3 groups give 9 items.

Check your answer

Multiply your result by the denominator part if possible: for frac{3}{4} of 12, check that 12 f7 4 = 3, then 3 d7 3 = 9. Also make sure the answer is less than the whole set when the fraction is less than 1.

Tip

If the set does not divide evenly, think carefully about the context of the exercise and count accurately from the equal groups shown or implied.