Subtracting fractions · Year 6
In Year 6 you learn: subtracting fractions with different denominators.
You can only subtract fractions when the pieces are the same size, so the denominators must match. If they don’t, change them to a common denominator first. With mixed numbers you may need to exchange a whole for fraction pieces.
Key facts
- Same denominator: add or subtract the tops. The bottom stays the same.
- Different denominators: first change both to a common denominator (the lowest common multiple is easiest). Then add or subtract.
- Never subtract the bottoms: 3/4 − 1/2 is not 2/2.
- Check a subtraction by adding: your answer plus the fraction you took away gives the fraction you started with.
- Simplify the answer at the end.
Worked examples
Example 1
Work out 5/6 − 1/6.
Answer: 2/3
Example 2
Work out 7/9 − 4/9.
Answer: 1/3
Example 3
A jug is 7/10 full of juice. Sam pours out 3/10 of a jug. How full is the jug now?
Answer: 2/5 full
Example 4
Work out 3/4 − 3/8.
Answer: 3/8
Example 5
Work out 4/5 − 1/3.
Answer: 7/15
Example 6
Sipho earns £12,000 a month. He spends 1/4 of it on rent and 1/3 on food. How much is left?
Answer: £5,000