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Year 5 - Maths

Explain how to identify a prime factor of a number

Understand and use the concept of factorisation (square and prime numbers)

Unit Summary

In this unit pupils will understand and use the concept of factorisation, explaining what a factor is and how to use arrays and multiplication/division facts to find them. They will identify prime numbers, square numbers and composite numbers.

Lesson Summary

You will learn to explain how to identify a prime factor of a number.

Key Notes

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

Vocabulary To Learn

  • 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.

Common Mistakes To Avoid

  • Pupils try to compose numbers additively using prime factors.

3 Quick Questions (With Answers)

1. Solve this in steps: explain the method from this lesson and why each step matters.

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

2. Use this key word in a maths sentence and explain it clearly. 'factor'

A factor is a whole number which exactly divides another whole number. Use this word when showing your method, then check your final answer is reasonable.

3. Spot and fix this common maths mistake.

Mistake: Pupils try to compose numbers additively using prime factors. Correction: 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.

More Lessons In This Unit

Browse all guides in the Year 5 Maths guide library.