Identifying Prime Numbers Worksheet | Key Stage 2 PDF Number ... - Free Printable

Let's solve each question in Section A of the worksheet step by step and explain how to identify multiples of 2, 3, 5, and 7.

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1) Which of these numbers are multiples of 2?

Numbers:
13, 8, 7, 25, 32, 40, 99, 81, 74, 15, 56, 27, 38, 73, 92, 100, 70

✔ Multiples of 2 (even numbers):
A number is a multiple of 2 if it is even, meaning its last digit is 0, 2, 4, 6, or 8.

So, circle these:
8, 32, 40, 74, 56, 38, 92, 100, 70

🔹 How do you know?
I know because multiples of 2 are even numbers, and even numbers end in 0, 2, 4, 6, or 8. I checked the last digit of each number.

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2) Which of these numbers are multiples of 3?

Numbers:
65, 13, 24, 42, 100, 51, 76, 91, 15, 88, 6, 28, 58, 67, 39, 45, 78

✔ Multiples of 3:
To check if a number is a multiple of 3, add up its digits. If the sum is divisible by 3, then the number is divisible by 3.

Let’s test each:

- 65 → 6+5 = 11 → not divisible by 3 ✘
- 13 → 1+3 = 4 → no ✘
- 24 → 2+4 = 6 → yes ✔
- 42 → 4+2 = 6 → yes ✔
- 100 → 1+0+0 = 1 → no ✘
- 51 → 5+1 = 6 → yes ✔
- 76 → 7+6 = 13 → no ✘
- 91 → 9+1 = 10 → no ✘
- 15 → 1+5 = 6 → yes ✔
- 88 → 8+8 = 16 → no ✘
- 6 → 6 → yes ✔
- 28 → 2+8 = 10 → no ✘
- 58 → 5+8 = 13 → no ✘
- 67 → 6+7 = 13 → no ✘
- 39 → 3+9 = 12 → yes ✔
- 45 → 4+5 = 9 → yes ✔
- 78 → 7+8 = 15 → yes ✔

✔ Circle these:
24, 42, 51, 15, 6, 39, 45, 78

🔹 Explain how you know:
I added the digits of each number. If the sum is divisible by 3, then the number is divisible by 3.

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3) Which of these numbers are multiples of 5?

Numbers:
65, 81, 97, 100, 13, 5, 72, 68, 25, 39, 50, 18, 27, 83, 40, 85, 1

✔ Multiples of 5:
A number is a multiple of 5 if it ends in 0 or 5.

Check each:
- 65 → ends in 5 → ✔
- 81 → ends in 1 → ✘
- 97 → ends in 7 → ✘
- 100 → ends in 0 → ✔
- 13 → ends in 3 → ✘
- 5 → ends in 5 → ✔
- 72 → ends in 2 → ✘
- 68 → ends in 8 → ✘
- 25 → ends in 5 → ✔
- 39 → ends in 9 → ✘
- 50 → ends in 0 → ✔
- 18 → ends in 8 → ✘
- 27 → ends in 7 → ✘
- 83 → ends in 3 → ✘
- 40 → ends in 0 → ✔
- 85 → ends in 5 → ✔
- 1 → ends in 1 → ✘

✔ Circle these:
65, 100, 5, 25, 50, 40, 85

🔹 Describe how you can tell:
I looked at the last digit. Numbers that end in 0 or 5 are multiples of 5.

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4) Which of these numbers are multiples of 7?

Numbers:
36, 14, 27, 77, 20, 58, 42, 81, 18, 35, 97, 65, 11, 5, 0, 63

✔ Multiples of 7:
We can divide each number by 7 and see if it divides evenly (no remainder), or recall known multiples.

Let’s check:

- 36 ÷ 7 = 5.14... → no ✘
- 14 ÷ 7 = 2 → yes ✔
- 27 ÷ 7 ≈ 3.85 → no ✘
- 77 ÷ 7 = 11 → yes ✔
- 20 ÷ 7 ≈ 2.85 → no ✘
- 58 ÷ 7 ≈ 8.28 → no ✘
- 42 ÷ 7 = 6 → yes ✔
- 81 ÷ 7 ≈ 11.57 → no ✘
- 18 ÷ 7 ≈ 2.57 → no ✘
- 35 ÷ 7 = 5 → yes ✔
- 97 ÷ 7 ≈ 13.85 → no ✘
- 65 ÷ 7 ≈ 9.28 → no ✘
- 11 ÷ 7 ≈ 1.57 → no ✘
- 5 ÷ 7 ≈ 0.71 → no ✘
- 0 ÷ 7 = 0 → yes ✔ (0 is a multiple of every number)
- 63 ÷ 7 = 9 → yes ✔

✔ Circle these:
14, 77, 42, 35, 0, 63

🔹 How did you decide?
I divided each number by 7 and checked if there was no remainder. Alternatively, I used my knowledge of multiplication facts (e.g., 7×2=14, 7×11=77, etc.). Also, 0 is a multiple of 7 because 7×0 = 0.

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✔ Final Answers Summary:

#### 1) Multiples of 2:
8, 32, 40, 74, 56, 38, 92, 100, 70

#### 2) Multiples of 3:
24, 42, 51, 15, 6, 39, 45, 78

#### 3) Multiples of 5:
65, 100, 5, 25, 50, 40, 85

#### 4) Multiples of 7:
14, 77, 42, 35, 0, 63

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This worksheet helps build number sense and understanding of divisibility rules — key skills for identifying prime numbers later on! 🎉