Success Homeschool

Primary 6 Mathematics · Prime, composite and square numbers

Name: ______________________

Date: ____________

1. Which of these numbers is prime?
- ☐ (a) 21
- ☐ (b) 27
- ☐ (c) 29
- ☐ (d) 33
2. Which of these numbers is composite?
- ☐ (a) 13
- ☐ (b) 17
- ☐ (c) 19
- ☐ (d) 51
3. Which of these is a square number?
- ☐ (a) 24
- ☐ (b) 36
- ☐ (c) 48
- ☐ (d) 50
4. Which statement about the number 1 is true?
- ☐ (a) It is prime.
- ☐ (b) It is composite.
- ☐ (c) It is neither prime nor composite.
- ☐ (d) It is both prime and composite.
5. How many factors does 18 have?
6. What is 7 squared (7²)?
7. What is the only even prime number?
8. How many prime numbers are there between 20 and 30?

Answer sheet

1. 29 — 29 has only two factors, 1 and 29. 21 = 3 × 7, 27 = 3 × 9 and 33 = 3 × 11 are composite.
2. 51 — 51 = 3 × 17, so it has more than two factors. 13, 17 and 19 are prime.
3. 36 — 36 = 6 × 6, so 36 counters can be arranged in a 6 × 6 square array.
4. It is neither prime nor composite. — 1 has only one factor, so it does not fit the definition of prime (exactly two factors) or composite (more than two factors).
5. 6 — The factor pairs are 1 × 18, 2 × 9 and 3 × 6, so the factors are 1, 2, 3, 6, 9 and 18: six factors.
6. 49 — 7 squared means 7 × 7 = 49.
7. 2 — 2 has exactly two factors, 1 and 2. Every other even number also has 2 as a factor, so it has more than two factors.
8. 2 — The prime numbers between 20 and 30 are 23 and 29. The others (21, 22, 24, 25, 26, 27, 28) are composite.