Maths Year 5 Fractions, decimals & %
Year 5 maths: adding and subtracting fractions, worked example and two common mistakes
Adding and subtracting fractions is a Year 5 maths topic. In the national curriculum’s words: Add and subtract fractions with the same denominator, and denominators that are multiples of the same number.
The explanation, example and questions are the ones Remelia uses in the app; the questions are not taken from any test paper.
Adding and subtracting fractions: the idea
When one denominator is a multiple of the other, scale the smaller one up so both match, then add or subtract the numerators.
How to do it
- Check whether one denominator divides into the other.
- Scale that fraction up.
- Add or subtract the numerators only.
- Simplify the answer.
A worked example
2/3 + 1/6 = 4/6 + 1/6 = 5/6.
Watch for
Adding denominators. 1/4 + 3/8 = 2/8 + 3/8 = 5/8, not 4/12.
Four questions on adding and subtracting fractions
-
Noor says: 2/3 + 3/9 = 5/12.
Is Noor right? Write the correct answer, not just yes or no.
Show the answer to question 1
Answer: 1 (also accept 9/9) · "No, 1" is right too; "No" on its own scores nothing
Why:
You cannot add the tops and the bottoms. Make the denominators the same first: 2/3 = 6/9, then 6/9 + 3/9 = 9/9 = 1.
Noor's answer was not right: the correct answer is 1.
-
1 − 2/6 = ?
- A 4/5
- B 2/3
- C 3/4
- D 5/6
Show the answer to question 2
Answer: B · 2/3
Why:
1 = 6/6. 6/6 − 2/6 = 4/6 = 2/3.
-
? + 3/4 = 10/12
What is the missing fraction? Write it in its simplest form.
Show the answer to question 3
Answer: 1/12
Why:
3/4 = 9/12. 10/12 − 9/12 = 1/12.
-
4/6 + 3/18 = ?
- A 5/12
- B 5/7
- C 7/8
- D 5/6
Show the answer to question 4
Answer: D · 5/6
Why:
6 goes into 18, so change 4/6 into 12/18.
12/18 + 3/18 = 15/18 = 5/6.
Answers
- 1. 1 (also accept 9/9) · "No, 1" is right too; "No" on its own scores nothing
- 2. B · 2/3
- 3. 1/12
- 4. D · 5/6
Two common mistakes in adding and subtracting fractions
When a wrong answer to a question like these matches one of these mistakes, the app says what the child seems to have done before they try again.
- Question 1, the answer 5/12: It looks as if you added the numerators and added the denominators. First make the denominators the same, then add only the numerators.
- Question 1, the answer 5/9: It looks as if you used the numerators before the fractions had the same denominator. Change one fraction first so both are cut into the same pieces.
More Year 5 maths
Remelia starts from what your child’s class has been taught. It practises maths for your child’s own year group, in short sessions, and brings back on later days what they got wrong.
Year 5 fractions, decimals & %, every objective with a question, and six fractions questions with the common mistakes.