Prime or composite
Numbers to 50
Name: Date:
Circle whether each number is prime or composite.
144PrimeComposite
210PrimeComposite
339PrimeComposite
425PrimeComposite
523PrimeComposite
619PrimeComposite
746PrimeComposite
821PrimeComposite
Free · Grade 4 · Numbers to 30, 50, or 100
Prime or composite worksheets
Working on prime or composite? Print this sheet as it is, or change the level and questions first. You can also answer it on screen — it is the same sheet either way.
- Answer key included
- Reopen this exact sheet
- Letter & A4 ready
Ready to printPrime or composite
The answer key prints on a separate page.
What's on this sheet
The sheets are built to defeat the shortcut, which is the only interesting thing about designing them. Every prime except 2 is odd, so a page whose composites are all even numbers can be answered at speed by a child who has learned nothing: call the evens composite, call the odds prime, score nearly full marks. So the odd composites are drawn as their own group and every page contains some — 9, 15, 21, 25, 33, 35, 49 are the numbers that make this a real question, and a sheet without them is testing odd and even while calling it primality.
Why this sheet works
The band is the difficulty, and it is not just about bigger numbers. Up to 30, a composite gives itself away to the 2, 3 and 5 times tables. Past 50 the sheet starts asking about 91 and 97, where the only honest method is dividing by each prime up to the square root — and testing every candidate up to 100 is exactly the range the standard names.