The “In Your Prime” Game is based on The Sieve of Eratosthenes, which is an ancient method of finding the prime numbers. Students will need to understand the rules of divisibility well in order to make judgments about whether the number they have landed on is prime or not. You may want to review the rules of divisibility with them before they begin trying to play this game.

As it says on the game board, it’s important for kids to remember that “1” is NOT a prime number. It’s a special case. Remind them that a prime number is an integer that has no integral factors but itself and 1. Based on this, the number 2 is prime because it can only be expressed as 2 x 1. The number 6 is not because it’s divisible by both 2 and 3.

Make sure that kids understand that the yellow and white squares on this gameboard don’t have any particular significance. The yellow tint is only a visual device to keep the numbers separated from each other. Therefore, prime numbers could be on a white square or on a yellow square.

After students have played this game a number of times, it’s great to wrap up with some summary questions related to patterns. Are there any columns that have no primes? Which column has the most number of primes? Are there any rows that have no primes? Which row has the greatest number of primes? This game is also a great springboard for some background history on Eratosthenes.

Common Core Mathematical Standard 6.NS Compute fluently with multi-digit numbers and find common factors and multiples.

Common Core Standards for Mathematical Practice
5. Use appropriate tools strategically.