A prime number can only be made one way in multiplication: 1 × itself. A number that can be made in more than one way is not prime.
For example, 5 can only be made as 1 × 5, so it is prime, but 6 can be made as 1 × 6 and also 2 × 3, so it is not prime.
This is a special multiplication table because it doesn't show you multiples of 1. The black boxes highlight the only prime numbers on this chart.
Can you find these numbers in the chart above. If it can be made in any way other than 1 × itself, it is not prime. If it can only be made as 1 × itself, it is prime so colour it in!