Dividing fractions
We divide by a fraction by multiplying by the fraction turned upside down: 2/3 ÷ 4/9 = 2/3 · 9/4 = 18/12 = 3/2. Check: 3/2 · 4/9 = 12/18 = 2/3, which is what we started with.
Watch Fox work it out on the board
Fox works one step at a time. Press play.
Solve your own task
Write the task. You get one step at a time.
What division means
12 ÷ 3 asks: how many threes fit into twelve? The same question works with fractions.
We want to know how many halves fit into three.
3 ÷
Each whole holds two halves. Three wholes hold 3 · 2 = 6 halves.
3 ÷
Small pieces fit in many times, so the answer is greater than three.
Why we flip the fraction
How many times does 3/4 fit into three wholes?
- Three wholes are 3 · 4 = 12 quarters. We multiply by the denominator.
- Twelve quarters are enough for 12 ÷ 3 = 4 groups of three. We divide by the numerator.
- Times four and divided by three is the same as times 4/3.
3 ÷
The fraction turned upside down is called the reciprocal.
The rule step by step
- Write whole numbers and mixed numbers as fractions: 5 = 5/1 and 1 1/2 = 3/2.
- Keep the first fraction.
- Change ÷ to · and flip the fraction we are dividing by.
- Multiply, and simplify if you can.
- Check: the answer times the fraction we divided by should give what we started with.
Example
Example 1:
We want to know how many times 4/9 fits into 2/3.
We keep 2/3, change ÷ to · and flip 4/9.
Numerator times numerator, denominator times denominator.
(2 · 9)/(3 · 4) =
Eighteen and twelve can both be divided by six.
So 4/9 fits in one and a half times.
3/2 · 4/9 = 12/18 = 2/3. We are back at 2/3, so the answer is correct.
Example 2: litre of juice shared equally between 5 glasses
We want to know how much juice each glass gets: 5/6 ÷ 5.
Five is 5/1. Flipped, it becomes 1/5.
Dividing by five is taking one fifth. We multiply.
(5 · 1)/(6 · 5) =
Five and thirty can both be divided by five.
5 · 1/6 = 5/6 litre, which is all the juice. Each glass gets 1/6 litre.
Pitfalls
Flipping the first fraction: 2/3 ÷ 4/9 becomes 3/2 · 4/9.
Flip the fraction after the division sign. The first one stays as it is: 2/3 · 9/4.
Thinking that dividing by 1/2 is like dividing by 2: 3 ÷ 1/2 = 1.5.
Dividing by a half is counting halves. Six halves fit into three wholes, so 3 ÷ 1/2 = 6.
Forgetting to flip a whole number: 3/4 ÷ 3 = 3/4 · 3 = 9/4.
Write 3 = 3/1 and flip it: 3/4 ÷ 3 = 3/4 · 1/3 = 3/12 = 1/4. If we share into three parts, the answer should be smaller.
Practise on your own
0 of 4 correct1Work out 2 ÷ .
2Work out . Give your answer in its simplest form.
3Work out .
4Work out . Give your answer as a fraction in its simplest form.
Common questions
Why does the answer get bigger when you divide by a fraction?
Dividing by a fraction less than one asks how many small pieces fit. More pieces fit than wholes, so the answer is bigger.
What is a reciprocal?
The fraction turned upside down. The reciprocal of 4/9 is 9/4, and 4/9 · 9/4 = 36/36 = 1.
How do you divide mixed numbers?
Rewrite them as fractions first. How many 1/4 litre glasses fit into 1 1/2 litres? 3/2 ÷ 1/4 = 3/2 · 4/1 = 12/2 = 6 glasses.
Can you divide numerator by numerator and denominator by denominator?
Yes, when they divide exactly: 6/8 ÷ 2/4 = (6 ÷ 2)/(8 ÷ 4) = 3/2. Otherwise flip and multiply is safer.
Read also
- Years 6–9Multiplying fractionsHow do you multiply fractions?
- Years 5–8Adding and subtracting fractionsHow do you add and subtract fractions?
- Years 4–7Equivalent fractions: expanding and simplifyingHow do you expand and simplify fractions?
- Years 8–9 and upper secondaryEquations with fractionsHow do you solve an equation with fractions?
Keep practising with Somokai
Free to start. Hints and explanations when you get stuck.
Start practising for freeFound a mistake? Get in touch