Let's watch a video about how we can use fractions to divide up a group of objects.

If you are unsure about fractions, look back at the chapters on fraction bars, fractions on the number line or fractions of shapes.

Unit fractions

When we use fractions it is sometimes about dividing a collection of items. To do this we use the:

denominator to divide the items into equal groups

numerator to select the number of groups

When we only select one of the groups (so the numerator is one) it is called a unit fraction.

For example, to find $\frac{1}{4}$14 of $12$12 items, we divide the collection into four equal groups ($3$3 in each group) and then select one of them. Like this:

Remember!

We use the denominator to divide the collection into equal groups.

We use the numerator to select the number of groups.

Try this question for yourself:

Worked example

Question 1:

Which of the following shows that $\frac{1}{2}$12 of these flowers have been selected?

A

B

C

Non-unit fractions

We can also select more than one group which are represented by non-unit fraction. These are fractions that have a number greater than one as the numerator (top number).

For example, to find five twelfths ($\frac{5}{12}$512) of $24$24 items, we use the denominator to divide the items into equal groups (twelve equal groups) and then we select five of the groups.

Like this:

When we divide the strawberries into twelve equal groups there are two in each group. We then select five of the groups, ten strawberries, to represent $\frac{5}{12}$512. Therefore $\frac{5}{12}$512 of $24=10$24=10

Try this question for yourself:

Worked example

Question 2:

Which of the following shows that $\frac{3}{4}$34 of these ice creams have been selected?

A

B

C

Remember!

To find a fraction of a quantity, you first divide by the denominator (to get the size of the equal groups), then you multiply by the numerator (to get the number of equal groups).