Year 5 Maths: Prime Numbers

What are Prime Numbers?

Hello, Year 5! Today, we are going to learn about prime numbers.

A prime number is a special kind of number. It has exactly two different factors: 1 and itself.

Examples of Prime Numbers

Let’s look at some examples:

• 2 is a prime number because its only factors are 1 and 2.
• 3 is also a prime number because its only factors are 1 and 3.
• 4 is not a prime number because it has three factors: 1, 2, and 4.

Key Rules for Identifying Prime Numbers

1. Two is the only even prime number! All other even numbers can be divided by 2, so they have more than two factors.
2. If a number ends in 0, 2, 4, 5, 6, or 8, it is not prime, except for 2.
3. A prime number is greater than 1.

Tips and Tricks

• To check if a number is prime, try dividing it by prime numbers smaller than it. If none divide evenly (without a remainder), then it is prime!
• Remember the first few prime numbers: 2, 3, 5, 7, 11, 13, 17, 19, 23, and 29.

Let’s Practice!

Now that you understand prime numbers, let’s do some questions!

Easy Questions (1-20)

1. Is 2 a prime number?
2. Is 3 a prime number?
3. Is 4 a prime number?
4. Is 5 a prime number?
5. Is 6 a prime number?
6. Is 7 a prime number?
7. Is 8 a prime number?
8. Is 9 a prime number?
9. Is 10 a prime number?
10. Is 11 a prime number?
11. List the first five prime numbers.
12. Is 12 a prime number?
13. Is 13 a prime number?
14. Is 14 a prime number?
15. Is 15 a prime number?
16. Is 16 a prime number?
17. Is 17 a prime number?
18. Is 18 a prime number?
19. Is 19 a prime number?
20. Is 20 a prime number?

Medium Questions (21-40)

21. How many prime numbers are there between 1 and 30?
22. Which is the smallest prime number?
23. Which is the largest prime number less than 20?
24. Is 23 a prime number?
25. Is 24 a prime number?
26. Is 29 a prime number?
27. List all the prime numbers between 10 and 30.
28. How many even prime numbers are there?
29. What is the sum of the first three prime numbers?
30. Is 31 a prime number?
31. Is 32 a prime number?
32. What are the factors of 37?
33. Is 39 a prime number?
34. What is the next prime number after 41?
35. Is 43 a prime number?
36. List the prime numbers between 1 and 50.
37. What is the product of the first two prime numbers?
38. Is 44 a prime number?
39. Is 45 a prime number?
40. Is 46 a prime number?

Hard Questions (41-60)

41. Why is 2 the only even prime number?
42. What is the difference between 53 and the next prime number?
43. Is 57 a prime number?
44. What is the sum of all prime numbers between 1 and 100?
45. How many prime numbers are there between 50 and 100?
46. Is 61 a prime number?
47. Is 62 a prime number?
48. What is the largest two-digit prime number?
49. If you add the first four prime numbers, what do you get?
50. Create a list of all prime numbers less than 50 and their factors.
51. Is 67 a prime number?
52. What do you notice about the factors of prime numbers?
53. Is 70 a prime number?
54. What is the next prime number after 73?
55. Are there more prime numbers less than 50 or more than 50?
56. Is 79 a prime number?
57. What is the prime factorization of 100?
58. Is 81 a prime number?
59. How many prime numbers are between 30 and 50?
60. Can you find a prime number that is also a Fibonacci number?

Answers and Explanations

Easy Questions Answers

1. Yes
2. Yes
3. No
4. Yes
5. No
6. Yes
7. No
8. No
9. No
10. Yes
11. 2, 3, 5, 7, 11
12. No
13. Yes
14. No
15. No
16. No
17. Yes
18. No
19. Yes
20. No

Medium Questions Answers

21. 10 (2, 3, 5, 7, 11, 13, 17, 19, 23, 29)
22. 2
23. 19
24. Yes
25. No
26. Yes
27. 11, 13, 17, 19, 23, 29
28. 1
29. 10 (2 + 3 + 5)
30. Yes
31. No
32. 1 and 37
33. No
34. 43
35. Yes
36. 15 (2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47)
37. 6 (2 × 3)
38. No
39. No
40. No

Hard Questions Answers

41. Because all other even numbers can be divided by 2.
42. 2 (55 is the next prime number)
43. No
44. 1060
45. 25
46. Yes
47. No
48. 97
49. 10 (2 + 3 + 5 + 7)
50. (2: 1, 2), (3: 1, 3), (5: 1, 5), (7: 1, 7), (11: 1, 11), (13: 1, 13), (17: 1, 17), (19: 1, 19), (23: 1, 23), (29: 1, 29), (31: 1, 31), (37: 1, 37), (41: 1, 41), (43: 1, 43), (47: 1, 47)
51. Yes
52. They only have two factors.
53. No
54. 79
55. More than 50
56. Yes
57. 2 × 2 × 5 × 5
58. No
59. 8
60. Yes (2, 3, 5, 13)

I hope you enjoyed learning about prime numbers! Keep practicing, and you’ll become a prime number expert!