In Numeracy, Year five have been learning about multiples, factors, prime numbers and prime factors. Here, the children are creating a table that will help them identify all the prime numbers less than 100.

- First we coloured in 1, because all prime numbers are greater than 1.
- Number 2 is a prime number. In fact it is the only even one. So we kept it but coloured in all the multiples of 2 (i.e even numbers).
- Number 3 is also a prime, so again we kept it and coloured in all the multiples of 3.
- The next number not coloured in was 5 (because 4 was already coloured in), so we kept it and coloured in all the multiples of 5.
- The final number left in the first row was 7 (it’s prime so we kept it) and coloured in all the multiples of 7.
- FINISHED! All the ‘surviving’ numbers that are not coloured in on the grid are PRIME NUMBERS!

So there you have it, how we worked out prime numbers on a 100 grid.