Math worksheet for identifying prime and composite numbers.

Let’s solve this step by step.

First, remember:
- A prime number has exactly two factors: 1 and itself.
- A composite number has more than two factors (so it can be divided evenly by numbers other than 1 and itself).
- The number 1 is neither prime nor composite, but none of the numbers here are 1.
- The smallest prime is 2 — it’s the only even prime.

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Part A: Write if each number is prime or composite.

1) 15 → Factors: 1, 3, 5, 15 → More than 2 → Composite

2) 89 → Let’s check: Not divisible by 2, 3, 5, 7. Next prime is 11 → 11×8=88, 11×9=99 → too big. So no divisors except 1 and 89 → Prime

3) 37 → Check divisibility: Not even, not divisible by 3 (3+7=10, not divisible by 3), not by 5, 7? 7×5=35, 7×6=42 → no. So → Prime

4) 70 → Even → divisible by 2 → also ends in 0 → divisible by 5 and 10 → definitely Composite

5) 93 → Sum of digits: 9+3=12 → divisible by 3 → 93 ÷ 3 = 31 → so factors include 3 and 31 → Composite

6) 19 → Only divisible by 1 and 19 → Prime

7) 2 → Only even prime → Prime

8) 21 → 3 × 7 = 21 → Composite

✔ Part A Answers:
1) Composite
2) Prime
3) Prime
4) Composite
5) Composite
6) Prime
7) Prime
8) Composite

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Part B: Circle all the prime numbers.

List:
13, 86, 5, 20, 71, 90,
95, 41, 29, 53, 8, 67

Check each:

- 13 → Prime ✔
- 86 → Even → Composite ✘
- 5 → Prime ✔
- 20 → Even → Composite
- 71 → Check: Not divisible by 2,3,5,7 (7×10=70, 7×11=77) → Prime ✔
- 90 → Ends in 0 → Composite ✘
- 95 → Ends in 5 → divisible by 5 → 95÷5=19 → Composite ✘
- 41 → Check: Not divisible by 2,3,5,7 (7×5=35, 7×6=42) → Prime ✔
- 29 → Prime ✔
- 53 → Check: Not divisible by 2,3,5,7 (7×7=49, 7×8=56) → Prime ✔
- 8 → Even → Composite ✘
- 67 → Check: Not divisible by 2,3,5,7 (7×9=63, 7×10=70) → Prime ✔

✔ Primes to circle: 13, 5, 71, 41, 29, 53, 67

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Part C: Circle all the composite numbers.

List:
66, 3, 82, 16, 9, 59,
47, 75, 97, 38, 61, 44

We want composites — so NOT primes.

Check each:

- 66 → Even → Composite ✔
- 3 → Prime ✘
- 82 → Even → Composite ✔
- 16 → Even → Composite ✔
- 9 → 3×3 → Composite ✔
- 59 → Check: Not divisible by 2,3,5,7 (7×8=56, 7×9=63) → Prime ✘
- 47 → Prime ✘
- 75 → Ends in 5 → divisible by 5 → 75÷5=15 → Composite ✔
- 97 → Check: Not divisible by 2,3,5,7,11 (11×8=88, 11×9=99) → Prime ✘
- 38 → Even → Composite ✔
- 61 → Prime ✘
- 44 → Even → Composite ✔

✔ Composites to circle: 66, 82, 16, 9, 75, 38, 44

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Final Answer:

A)
1) Composite
2) Prime
3) Prime
4) Composite
5) Composite
6) Prime
7) Prime
8) Composite

B) Prime numbers: 13, 5, 71, 41, 29, 53, 67

C) Composite numbers: 66, 82, 16, 9, 75, 38, 44