Adding & subtracting fractions
Adding & subtracting: same denominator
When two fractions have the same denominator, you add or subtract the numerators and keep the denominator the same.
The rule
1. Check the denominators are the same. 2. Add (or subtract) the numerators. 3. Keep the denominator unchanged.
Worked examples
Adding
- Work out 1/9 + 3/9.
- Add the numerators: 1 + 3 = 4.
- Keep the denominator 9.
Answer: 1/9 + 3/9 = 4/9
Subtracting
- Work out 5/6 − 2/6.
- Subtract the numerators: 5 − 2 = 3.
- Keep the denominator 6.
Answer: 5/6 − 2/6 = 3/6
Where you see this in real life
- Working out how many slices of a cake (cut into equal pieces) have been eaten.
- Adding up parts of a pizza that friends have eaten.
- Finding how much of a chocolate bar is left.
Key words
- Numerator
- The top number of a fraction — how many parts you have.
- Denominator
- The bottom number — how many equal parts the whole is split into.
- Fraction
- A number that shows part of a whole.