Unit Fractions

We use division to help us calculate a fraction of a quantity.

So if we want to find 1/3 of a quantity we divide the quantity by 3. If we want to find 1/2 of a quantity, we divide the quantity by 2. What if we want to find 1/4 of a quantity?

Worked Example

What is 1/5 of £30?

Exercise 1

General Fractions

If the numerator of a fraction is not 1, we need to use multiplication as well as division

Worked Example

What is 3/4 of 36?

Exercise 2

Working Backwards

Sometimes we know what fraction of a quantity we have and want to work backwards to calculate the original quantity. So instead of dividing, we multiply (and instead of multiplying we divide)

Worked Example

The petrol tank in Sasha’s car is 2/3 full and has 40 litres in it. How much would be in if it were full?

Exercise 3

Answers