80 Important Questions – Playing with Numbers
1. What is the smallest prime number?
Solution: The smallest prime number is 2.
2. What is the LCM of 12 and 18?
Solution: LCM = 36.
3. Find the HCF of 48 and 180.
Solution: HCF = 12.
4. Check if 315 is divisible by 9.
Solution: Yes, 315 is divisible by 9.
5. Write the prime factorization of 100.
Solution: 100 = 22 × 52.
6. What is the sum of the first five prime numbers?
Solution: 2 + 3 + 5 + 7 + 11 = 28.
7. Find the number of factors of 36.
Solution: The factors of 36 are 1, 2, 3, 4, 6, 9, 12, 18, 36. Total = 9 factors.
8. What is the greatest common factor of 20 and 30?
Solution: GCF = 10.
9. How many multiples of 5 are there between 1 and 50?
Solution: There are 10 multiples (5, 10, 15, …, 50).
10. Is 97 a prime number?
Solution: Yes, 97 is a prime number.
11. Find the smallest 4-digit number.
Solution: The smallest 4-digit number is 1000.
12. What is the largest 3-digit number?
Solution: The largest 3-digit number is 999.
13. What is the sum of the digits of 546?
Solution: 5 + 4 + 6 = 15.
14. What is 7 × 11?
Solution: 7 × 11 = 77.
15. Check if 129 is divisible by 3.
Solution: Yes, 129 is divisible by 3.
16. Find the HCF of 36 and 60.
Solution: HCF = 12.
17. Find the LCM of 15 and 25.
Solution: LCM = 75.
18. What is the next prime number after 13?
Solution: The next prime number is 17.
19. How many digits are in the number 10000?
Solution: There are 5 digits.
20. Write the prime factorization of 36.
Solution: 36 = 22 × 32.
21. What is the smallest multiple of 9 greater than 50?
Solution: The smallest multiple is 54.
22. What is the sum of 9 and 8?
Solution: 9 + 8 = 17.
23. What is the product of the first four even numbers?
Solution: 2 × 4 × 6 × 8 = 384.
24. Find the prime factorization of 48.
Solution: 48 = 24 × 3.
25. Is 4 a prime number?
Solution: No, 4 is not a prime number.
26. What is the sum of the first ten natural numbers?
Solution: 1 + 2 + … + 10 = 55.
27. Find the smallest odd number greater than 10.
Solution: The smallest odd number is 11.
28. What is the product of 12 and 12?
Solution: 12 × 12 = 144.
29. What is the LCM of 8 and 12?
Solution: LCM = 24.
30. What is the HCF of 24 and 36?
Solution: HCF = 12.
31. Is 49 a prime number?
Solution: No, 49 is not a prime number.
32. How many prime numbers are there between 1 and 20?
Solution: There are 8 prime numbers (2, 3, 5, 7, 11, 13, 17, 19).
33. What is the smallest number divisible by both 5 and 6?
Solution: The smallest number is 30.
34. What is 6 raised to the power of 2?
Solution: 62 = 36.
35. Find the sum of 25 and 35.
Solution: 25 + 35 = 60.
36. What is the largest even number less than 100?
Solution: The largest even number is 98.
37. Find the next multiple of 10 after 120.
Solution: The next multiple is 130.
38. What is the product of the digits of 123?
Solution: 1 × 2 × 3 = 6.
39. Find the HCF of 81 and 27.
Solution: HCF = 27.
40. Is 81 a perfect square?
Solution: Yes, 81 is a perfect square (9 × 9).
41. What is the sum of the angles in a triangle?
Solution: The sum is 180 degrees.
42. What is the smallest 5-digit number?
Solution: The smallest 5-digit number is 10000.
43. Write the prime factorization of 60.
Solution: 60 = 22 × 3 × 5.
44. What is the difference between the largest and smallest 2-digit numbers?
Solution: 99 – 10 = 89.
45. Find the next prime number after 29.
Solution: The next prime number is 31.
46. What is the product of 7 and 9?
Solution: 7 × 9 = 63.
47. What is the HCF of 48 and 180?
Solution: HCF = 12.
48. What is the LCM of 6 and 8?
Solution: LCM = 24.
49. Is 121 a perfect square?
Solution: Yes, 121 is a perfect square (11 × 11).
50. What is the smallest prime number greater than 20?
Solution: The smallest prime number is 23.
51. Find the sum of 15 and 25.
Solution: 15 + 25 = 40.
52. What is the largest 4-digit number?
Solution: The largest 4-digit number is 9999.
53. What is the prime factorization of 24?
Solution: 24 = 23 × 3.
54. What is the difference between the largest and smallest prime numbers under 20?
Solution: 19 – 2 = 17.
55. What is the next multiple of 7 after 21?
Solution: The next multiple is 28.
56. Is 77 a prime number?
Solution: No, 77 is not a prime number.
57. What is the sum of the digits of 789?
Solution: 7 + 8 + 9 = 24.
58. How many factors does 60 have?
Solution: The factors are 1, 2, 3, 4, 5, 6, 10, 12, 15, 20, 30, 60. Total = 12 factors.
59. What is the smallest even number greater than 0?
Solution: The smallest even number is 2.
60. Find the prime factorization of 42.
Solution: 42 = 2 × 3 × 7.
61. What is the LCM of 3 and 5?
Solution: LCM = 15.
62. Is 15 a prime number?
Solution: No, 15 is not a prime number.
63. What is the sum of the first five odd numbers?
Solution: 1 + 3 + 5 + 7 + 9 = 25.
64. What is the product of 4 and 5?
Solution: 4 × 5 = 20.
65. How many multiples of 2 are there between 1 and 100?
Solution: There are 50 multiples (2, 4, …, 100).
66. What is the sum of 100 and 200?
Solution: 100 + 200 = 300.
67. What is the smallest number divisible by both 3 and 4?
Solution: The smallest number is 12.
68. What is the largest prime number under 30?
Solution: The largest prime number is 29.
69. Find the prime factorization of 36.
Solution: 36 = 22 × 32.
70. What is the product of 8 and 9?
Solution: 8 × 9 = 72.
71. What is the LCM of 10 and 15?
Solution: LCM = 30.
72. Is 30 a prime number?
Solution: No, 30 is not a prime number.
73. What is the sum of the angles in a quadrilateral?
Solution: The sum is 360 degrees.
74. What is the largest 2-digit number?
Solution: The largest 2-digit number is 99.
75. What is the smallest prime number greater than 50?
Solution: The smallest prime number is 53.
76. Find the sum of 12 and 18.
Solution: 12 + 18 = 30.
77. What is the smallest number that is a multiple of both 2 and 5?
Solution: The smallest number is 10.
78. What is the HCF of 100 and 200?
Solution: HCF = 100.
79. What is the prime factorization of 72?
Solution: 72 = 23 ×
32.
80. Is 64 a perfect square?
Solution: Yes, 64 is a perfect square (8 × 8).
