 # Fractions of Amounts. How to Find a Fraction of a Number. Math Help.

To find a fraction of an amount all you need to do is divide the amount by the denominator of the fraction, and multiply this answer by the numerator of the fraction. To help you out, try remembering the rule:

“Divide by the bottom and times by the top”

Example 1

What is 4/5 of \$30?

First work out:

30 ÷ 5 = 6                             (this gives 1/5 of \$30)

Then times this answer by the numerator (top number of the fraction).

6 × 4 = \$24                           (this gives 4/5 of \$30)

Example 2

What is 2/7 of \$42?

Again, first divide the amount of cash by the denominator (the bottom of the fraction).

42 ÷ 7 = 6                             (this gives 1/7 of \$42)

Now times this answer by the top.

6 × 2 = \$12                           (this gives 2/7 of \$42)

Example 4

Decrease \$30 by 2/5.

First we need to work out 2/5 of \$30.

30 ÷ 5 = 6

6 × 2 = \$12

Now since we are doing a fraction decrease question we need to take \$12 from \$30.

This gives a final answer of \$18.

Example 4

Increase \$50 by 3/5.

First we need to work out 3/5 of \$50.

50 ÷ 5 = 10

10 × 3 = \$30

Now since we are doing a fraction increase question we need to add \$30 to \$50.

This gives a final answer of \$80.

Example 5

There are 350 people in the local supermarket. 3/10 of the people in the supermarket are male. How many males and females are at the supermarket?

To work out the amount of males at the supermarket we need to find 3/10 of 350.

Do this by dividing by the bottom and multiplying by the top.

350 ÷ 10 = 35

35 × 3 = 105 males.

Therefore, there are 105 males at the supermarket.

Now to find the amount of females at the supermarket we need to take 105 off 350. This gives an answer of 245 people who are females.

So that is all you need to know. If you are working out a fraction of an amount, all you need to do is divide by the bottom and multiply the top.