Printable Prime and Composite Numbers Worksheets
Prime and composite number worksheets teach 4th grade students to classify numbers based on having exactly two factors or more than two. These printable sheets feature factor count grids and answer keys.
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Structured, printable skill sheets with step-by-step guidance for Prime and Composite Numbers.
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About Prime and Composite Numbers
What this skill is
A prime number is a whole number greater than 1 that has exactly two distinct factors: 1 and itself (like 2, 3, 5, 7, 11). A composite number has more than two factors.
When children learn it
Determining whether a given whole number in the range 1-100 is prime or composite is a core 4th grade standard (CCSS 4.OA.B.4).
Teaching Tips
- Use tiles or pennies: try to arrange 7 pennies into a neat rectangle with more than one row. You can only make a single line of 1 x 7, meaning 7 is PRIME. With 8 pennies, you can make a 2 x 4 box, meaning 8 is COMPOSITE.
Common Mistakes
- Thinking 1 is a prime number (1 is neither prime nor composite because it has only one factor).
- Thinking all odd numbers are prime, forgetting that numbers like 9, 15, and 21 are composite.
- Forgetting that 2 is the only even prime number.