Year 5 Prime Numbers, Factors, Squares and Cubes: lesson and practice

By the end of this chapter you will be able to

• Find multiples of a number, common multiples of two numbers and the lowest common multiple, and solve problems about things that repeat
• Use the tests of divisibility for 2, 3, 4, 5, 6, 8, 9, 10, 25 and 100
• Find all the factor pairs of a number in order, and find common factors and the highest common factor of two numbers
• Know prime and composite numbers, remember the primes up to 19 and decide whether a number up to 100 is prime
• Write a number up to 100 as a product of prime factors using a factor tree
• Know square numbers (up to 12 × 12 and beyond) and cube numbers, and use the ² and ³ notation
• Solve number-clue puzzles and reasoning problems: always, sometimes, never; prove it; spot the mistake

You should already know

• Times tables up to 12 × 12 and the related division facts (Year 4)
• Factor pairs and square numbers (Year 4 Chapter 3)
• Counting in steps of 2, 3, 4, 5, 6, 7, 8, 9, 10, 25
• Multiplying and dividing in your head (Chapters 4 and 5 build on this)

Where this leads

• Multiplication with factors and squares (Chapter 4)
• Equivalent fractions and simplifying (Chapter 6)
• Area of squares and volume of cubes (Chapter 8)
• Highest common factor, lowest common multiple and prime factorisation in Year 6 and secondary school