Dividing by unit fractions
Home learning focus
In this lesson you will learn how to divide by a unit fraction.
This lesson includes:
- one slideshow lesson
- one downloadable activity
A unit fraction is a fraction where the numerator is 1.
What does it mean to divide by a fraction?
You can think of 20 ÷ 10 as asking how many 10s are there in 20.
The same thing applies when you are dividing by fractions, so for example you can think of 4 ÷ ½ as asking how many halves are there in 4.
You can see that the 4 whole circles below are made up of 8 halves.
Now let's think about this sum. You need to work out how many quarters there are in 3 halves.
Here you have 3 halves of a whole circle.
Splitting this into quarters of the whole circle, you can see there are 6 quarters in 3 halves.
So the answer to the calculation is 6!
How many eighths are there in three eighths?
As you can see, the answer to the calculation is:
3/8 ÷ 1/8 = 3
How many eighths are there in one quarter?
How many eighths are there in three quarters?
As you can see, the answers to these calculations are:
1/4 ÷ 1/8 = 2 and
3/4 ÷ 1/8 = 6
What other method can you use?
The following slides from Numerise will show you a method for dividing by fractions without relying on images:
- keep the first value the same
- change the ÷ for a ×
- flip the second fraction
There's more to learn
Have a look at these other resources around the BBC and the web.