Adding fractions · Year 8
In Year 8 you learn: adding fractions in problems.
You can only add fractions when the pieces are the same size, so the denominators must match. If they don’t, change the fractions to equivalent fractions with a common denominator first, then add the numerators.
Key facts
- Different denominators: first change both to a common denominator (the lowest common multiple is easiest). Then add or subtract.
- Mixed numbers: add the wholes and the fractions separately, or turn both into improper fractions.
- If the answer is an improper fraction, you can write it as a mixed number: 19/12 = 1 7/12.
Worked examples
Example 1
Work out 2/3 + 1/4.
Answer: 11/12
Example 2
Work out 3/4 + 5/6.
Answer: 1 7/12
Example 3
Work out 1 3/5 + 2 2/3.
Answer: 4 4/15
Example 4
Work out 1 5/6 + 2 3/4.
Answer: 4 7/12
Example 5
A path is 2 3/4 km long. Ana walks the path, then another 1 2/3 km to the shop. How far does she walk altogether?
Answer: 4 5/12 km