This activity is 'The Sieve of Eratosthenes' method for finding the prime numbers below 100. The user has to following the instructions provided on top. i.e. First click on 1, then click on the multiples of 2. Once all the multiples of 2 are completed, they disappear. Similarly click on the multiples of 3, 5 and 7 one after the other. Once all the multiples of 7 is finished, the numbers left over are prime numbers below 100.