To find a fraction of a number, divide by the denominator and multiply by the numerator. 2/5 of 20: 20 ÷ 5 = 4, then 4 × 2 = 8.
This is the same as multiplying the fraction by the number: 2/5 × 20 = 40/5 = 8. Fractions of amounts appear in real life all the time, such as 3/4 of a class or 2/3 of a bag of sweets.
You can work backwards too. If 3/4 of a number is 30, then 1/4 is 10, so the whole number is 40.
Worked example
What is 3/8 of 48?
- 48 ÷ 8 = 6.
- 6 × 3 = 18.
Answer:18
Key words
- of
- means multiply in fraction questions
- denominator
- how many equal parts
- numerator
- how many parts you take
Practise this
New questions every time.
Common Core-referenced: 5.NF.B.4a