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KS2 Maths textbook

Year 6 HCF, LCM and Prime Numbers: lesson and practice

  • Strand Number
  • Level Year 6
  • Practice 97 questions with step-by-step solutions

National Curriculum for England, Key Stage 2 mathematics, Year 6. Content: Identify common factors, common multiples and prime numbers, Use factor trees and prime factors, including index form, to write a number as a product of primes, Find the lowest common multiple (LCM) and the highest common factor (HCF) of two or more numbers, Know the prime numbers up to 100 and establish whether a number up to 100 is prime.

Open Year 6 chapter

By the end of this chapter you will be able to

  • Find all the factors of a number, and the common factors and highest common factor (HCF) of two numbers
  • Find common multiples and the lowest common multiple (LCM) of two or three numbers
  • Recognise prime numbers, and know the primes up to 100
  • Write a number as a product of prime factors using a factor tree, and in index form
  • Use prime factors to find the HCF and the LCM
  • Choose between the HCF and the LCM to solve problems, and explain whether statements are always, sometimes or never true

You should already know

  • Factor pairs and multiplication facts (Year 5, Chapter 3)
  • Multiples, prime numbers, prime factors and factor trees to 19 and 100 (Year 5, Chapter 3)
  • Times tables up to 12 × 12 and the related division facts

Where this leads

  • Equivalent fractions and simplifying fractions using common factors (Chapter 4)
  • Writing a fraction in its simplest form with the HCF (Chapter 4)
  • Ratio and sharing in equal parts (Chapter 7)
  • Prime factors and the HCF and LCM in algebra and secondary school

Lessons in this chapter

  1. 3.1 Common factors and the highest common factor
  2. 3.2 Common multiples and the lowest common multiple
  3. 3.3 Prime numbers up to 100
  4. 3.4 Factor trees, prime factors and index form
  5. 3.5 HCF and LCM using prime factors
  6. 3.6 Problems and reasoning with factors, multiples and primes
  7. Summary and key words
  8. Check-up and SATs-style questions

Read the whole chapter on one page (good for printing).

Practise with real exam questions

The DfE publishes every past KS2 test, with mark schemes, for free.

KS2 Maths past papers