New
New
Year 5

Explain how to identify a prime factor of a number

I can explain how to identify a prime factor of a number.

New
New
Year 5

Explain how to identify a prime factor of a number

I can explain how to identify a prime factor of a number.

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Lesson details

Key learning points

  1. All numbers can be written as a product of 2 or more prime numbers.
  2. A prime factor is a factor of a number which is prime.

Common misconception

Pupils try to compose numbers additively using prime factors.

Ensure pupils are confident with finding the factors of a number first before extending to finding prime factors of known factors. Give time to building numbers with prime factors in arrays to help emphasise their multiplicative composition.

Keywords

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

  • Prime factor - A prime factor is a factor of a number that is a prime number.

You might like to explore how prime factors are applied in the making and breaking of secret codes based on numbers. This is known as 'encryption' or 'cryptography'.
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).

Video

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6 Questions

Q1.
Match the number to the correct type.
Correct Answer:Prime number,3

3

Correct Answer:Composite number,6

6

Correct Answer:Square number,4

4

Q2.
True or false: 19 is a prime number.
Correct answer: True
False
Q3.
Tick the prime numbers.
Correct answer: 3
Correct answer: 7
9
Correct answer: 17
21
Q4.
Complete: 4 × 2 × 3 =
Correct Answer: 24, twenty four
Q5.
What square number is represented by this incomplete factor bug?
An image in a quiz
Correct Answer: 36
Q6.
Match the expression to the correct product.
Correct Answer:4 × 5 × 5,100

100

Correct Answer:4 × 1 × 3,12

12

Correct Answer:4 × 3 × 5,60

60

Correct Answer:4 × 8 × 2,64

64

6 Questions

Q1.
True or false: 25 is a prime number.
True
Correct answer: False
Q2.
Tick the prime numbers.
9
Correct answer: 11
12
15
Correct answer: 17
Q3.
What are the prime factors shown in this factor bug?
An image in a quiz
1, 2, 3, 5, 6, 15
1, 2, 3, 5
Correct answer: 2, 3, 5
2, 3, 5, 6
Q4.
The factor bug shows the factors of 16 Which of the calculations below correctly shows 16 decomposed into prime factors?
An image in a quiz
2 × 4 × 8 = 16
2 × 2 × 4 = 16
Correct answer: 2 × 2 × 2 × 2 = 16
Q5.
The factor bug shows the factors of 30 Which of the calculations below correctly shows 30 decomposed into prime factors?
An image in a quiz
Correct answer: 2 × 3 × 5 = 30
2 × 2 × 10 = 30
2 × 3 × 5 × 6 = 30
Q6.
What is the missing prime factor? 51 = 3 ×
Correct Answer: 17, seventeen