Primary 4 maths · Fractions · About 10 minutes
Find a fraction of a set
Identify the amount that acts as the whole, then one part, then the selected parts.
Start the interactive lesson →Practise: Fraction treasure
What you will learn
- Find a fraction of a set
Models used: number sentences, stories, tables.
Before you start
Find a fraction of a group
Here are 12 counters. We want two thirds of them.
Each dot stands for one object. A full row holds five; two full rows make ten.
Here are 12 counters. We want two thirds of them.
There are 3 groups, with 4 objects in each group. Count a group before counting them all.
Thirds means three equal groups. Each group has 4 counters.
4 + 4 + 4 = 3 × 4 = 12
There are 2 groups, with 4 objects in each group. Count a group before counting them all.
Keep two of those groups. Two groups of four make eight.
2/3 of 12 = 8
4 + 4 = 2 × 4 = 8
What did the picture help us see?
Keep two of those groups. Two groups of four make eight.
Worked example: A new example, together
Find 2/4 of 12.
| Equal groups | In each group | Parts needed |
|---|---|---|
| 4 | 3 | 2 |
Share into denominator-many parts, then select numerator-many. Read each value with the heading above its column.
Identify the amount that acts as the whole, then one part, then the selected parts.
A fraction of a amount scales that quantity by the fraction.
Share into denominator-many parts, then select numerator-many Equal groups In each group Parts needed 4 3 2 Share into denominator-many parts, then select numerator-many. Read each value with the heading above its column.
A fraction of an amount means divide by 4, then take 2 of those parts.
Share into denominator-many parts, then select numerator-many Equal groups In each group Parts needed 4 3 2 Find 2/4 of 12.
6
Share into denominator-many parts, then select numerator-many. Read each value with the heading above its column.
12 ÷ 4 × 2.
Share into denominator-many parts, then select numerator-many Equal groups In each group Parts needed 4 3 2 Share into denominator-many parts, then select numerator-many. Read each value with the heading above its column.
The amount is 6.
Share into denominator-many parts, then select numerator-many Equal groups In each group Parts needed 4 3 2 Share into denominator-many parts, then select numerator-many. Read each value with the heading above its column.
Check the result against the question we started with.
The selected amount divided by 12 equals 2/4.
We found 6. A fraction of a amount scales that quantity by the fraction.
Share into denominator-many parts, then select numerator-many Equal groups In each group Parts needed 4 3 2
Common mistakes to discuss
- Dividing by the numerator. Divide by the denominator to find one part, then take as many as the numerator asks. 2/3 of 12 is 12 ÷ 3 × 2 = 8.
Check your understanding
- Find a fraction of a set
- explain fraction multiplication as selecting a share of an amount
- check the answer against the original quantities and units
Explain your reasoning to an adult, then try a fresh question in the interactive lesson. A result from one attempt is not proof of lasting mastery.
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