As with multiples, the children should already know what prime numbers are. Complete the BBC Bitesize activity and watch the Corbettmaths video. They could also watch around the first eight minutes of last Monday's BBC Bitesize programme but they don't have to. They should then work through the different activities. To identify the prime numbers on the first activity, they could use a 'sieving' method which we used in class at the start of P7: cross out 1 as 1 isn't considered to be a prime number; shade/colour all the multiples of 2; shade/colour any multiples of 3 still left; shade/colour any multiples of 5 still left and, finally, shade/colour any multiples of 7 still left (watch out for a couple in the 90s!) If this is done correctly, all the unshaded/uncoloured numbers are prime numbers.