This PPT and worksheet: Sieve of Eratosthenes was designed to help lower attaining Year 5 pupils learn about prime numbers. The activity within the presentation are suitable for a number of age rangers from upper Key Stage 2 to Year 7 and will help children identify prime number to 100. Prime numbers are special numbers, greater than 1, that have exactly two factors, themselves and 1. In this PPT the children are introduced to prime numbers with the Sieve of Eratosthenes in a scene using the characters from Transformers to unlock the prime numbers to 100 before it is too late… I’ve used this resource with both Year 5 and Year 6 students and you can make this exercise more interesting by asking them to colour in the prime numbers within a specific time limit.