New
New
Year 5

# Explain how to identify a prime number or a composite number

I can explain how to identify a prime number or a composite number.

New
New
Year 5

# Explain how to identify a prime number or a composite number

I can explain how to identify a prime number or a composite number.

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## Lesson details

### Key learning points

1. A prime number has only 2 factors, 1 and itself.
2. A composite number is a number with more than 2 factors.

### Common misconception

Every number has one and itself as a factor, so every number is a prime number.

Ensure pupils explore the different arrangements that numbers can make with tiles in arrays. Point out that the numbers which cannot be arranged in any way except for one row or column are prime numbers.

### Keywords

• Factor - A factor is a whole number which exactly divides another whole number.

• Prime number - A prime number is a whole number greater than one which has exactly two factors.

• Composite number - A composite number is a whole number which has more than two factors.

• Square number - A square number is the result of multiplying an integer (not a fraction) by itself.

Allow pupils to investigate the possible arrays for each number with each other and encourage them to record their findings in a way that can be communicated to others easily.
Teacher tip

### Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

## Starter quiz

### 6 Questions

Q1.
Match the expression to the correct square number.

4

9

121

64

Q2.
What square number is represented by this incomplete factor bug?
Correct Answer: 100, one hundred, hundred
Q3.
What is the missing factor of 38 from this list? 1, 2, 19
Q4.
The number 12 has factors.
Q5.
The number 30 has factors.
Q6.
Tick the numbers which are factors of both 15 and 20
2
10
15

## Exit quiz

### 6 Questions

Q1.
Exactly how many factors does a prime number have?
1
4
It depends on the prime number.
Q2.
Match the number to the correct type.

13

12

16

Q3.
What is the next prime number after 13?
Q4.
True or false: 27 is a prime number.
True
Q5.
Select the composite numbers.
2