4th Grade Prime Numbers: Problems and Activities

How to Help Your 4th Grader Identify Prime Numbers

A prime number is a whole number, or integer, that cannot be divided by any number except itself and one. For instance, five is a prime number. A composite number is an integer that can be divided by at least one whole number other than one and itself. So, four is a composite number because it can be divided by one, itself and two.

If your child struggles with identifying prime and composite numbers, it could be that he or she doesn't understand the difference between the terms. If this is the case, you might have your child define 'prime' and 'composite' in his or her own words in a math notebook. This will provide an easy reference in class and at home.

Once you're confident that your child knows what prime and composite numbers are, you can play a game to review. Place a deck of cards upside down on the table, and take turns flipping over a card. If it's a prime number, and you or your child correctly identify it as such, you get to keep the card. Whoever has more prime numbers by the end of the deck wins. This is a fast-paced, repetitive game, which will help your child become familiar with the concept of prime versus composite numbers.

Practice with Prime Numbers

1. List factors for the numbers 22 and 23. Then, identify each number as a prime or composite number.

For 22, the factors are 1, 2, 11 and 22, so it's a composite number. The factors for 23 are 1 and 23, so it's a prime number.

2. Is one a prime number or a composite number?

One isn't considered either a prime or composite number. This is a trick question; however, it's an important fact for your child to know.

3. List all the prime numbers through 20.

The prime numbers include 2, 3, 5, 7, 11, 13, 17 and 19.

4. Is 60 a prime number? Why or why not?

This type of question will allow your child to define prime numbers in his or her own words. In this case, 60 is not a prime number because it has factors other than 60 and one, which include 2, 3, 4, 5, 6, 10, 12, 15, 20 and 30.

5. The number x is a prime number between 25 and 30. What number is x?

The only prime number between 25 and 30 is 29. Questions like this one may make the material more entertaining for your child.