Year 5

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We can work out which numbers less than 100 are prime numbers

Year 5 Unit 17

What we are learning:

  • Prime numbers are numbers that can only be divided by 1 and themselves without a remainder.
  • The first prime number is therefore the number 1 itself.
  • The next one is 2 because it can only be divided (without a remainder) by 1 and 2.
  • The next one is 3 because it can only be divided by 1 and 3.
  • The next ones are 5, 7, 11, 13, 17, 19……
  • Apart from the number 2, all prime numbers are odd, but not all odd numbers are prime!

Activities you can do at home:

Explore all the prime numbers you can find together up to 100. Be careful to check that they are prime, and that nothing else will divide into them other than 1 and the number itself.

You need to know your tables to work out which numbers are prime!

Good questions to ask:

Can you explain what a prime number is?
Is 5 a prime number? How do you know?
Can 15 be a prime number? Why not?

If your child:

Cannot identify which numbers are prime
Take a low prime number, e.g. 13 and explore which other number will go into it without leaving a remainder. The answer will be 1 and 13. Now try 12, where you will find that 1, 2, 3, 4, 6 and 12 all go into it without leaving a remainder

Knows or can work out all the prime numbers to 100
Look for prime numbers over 100 together. How does your child set about finding them?


Activity sheet PDF

Extension Activity

Please use this activity when you think your child understands the unit of work. It will deepen and extend your child’s understanding of this unit.


Extension activity (PDF)

Extension activity answers (PDF)