Test: HCF - Class 8 MCQ

To find the HCF, we can list the factors of both numbers and find the highest common factor. The factors of 24 are 1, 2, 3, 4, 6, 8, 12, and 24. The factors of 36 are 1, 2, 3, 4, 6, 9, 12, 18, and 36. The highest common factor is 12, so the correct answer is option (c) 6.

The factors of 15 are 1, 3, 5, and 15. The factors of 25 are 1, 5, and 25. The highest common factor is 5, so the correct answer is option (b) 5.

The factors of 36 are 1, 2, 3, 4, 6, 9, 12, 18, and 36. The factors of 48 are 1, 2, 3, 4, 6, 8, 12, 16, 24, and 48. The highest common factor is 12, so the correct answer is option (c) 12.

The factors of 42 are 1, 2, 3, 6, 7, 14, 21, and 42. The factors of 56 are 1, 2, 4, 7, 8, 14, 28, and 56. The highest common factor is 14, so the correct answer is option (c) 14.

The factors of 72 are 1, 2, 3, 4, 6, 8, 9, 12, 18, 24, 36, and 72. The factors of 90 are 1, 2, 3, 5, 6, 9, 10, 15, 18, 30, 45, and 90. The highest common factor is 18, so the correct answer is option (d) 18.

The factors of 64 are 1, 2, 4, 8, 16, 32, and 64. The factors of 128 are 1, 2, 4, 8, 16, 32, 64, and 128. The highest common factor is 64, so the correct answer is option (d) 64.

The factors of 20 are 1, 2, 4, 5, 10, and 20. The factors of 30 are 1, 2, 3, 5, 6, 10, 15, and 30. The highest common factor is 10, so the correct answer is option (c) 10.

The factors of 81 are 1, 3, 9, 27, and 81. The factors of 99 are 1, 3, 9, 11, 33, and 99. The highest common factor is 9, so the correct answer is option (b) 9.

The factors of 48 are 1, 2, 3, 4, 6, 8, 12, 16, 24, and 48. The factors of 64 are 1, 2, 4, 8, 16, 32, and 64. The highest common factor is 16, so the correct answer is option (d) 16.

The factors of 17 are 1 and 17. The factors of 23 are 1 and 23. The highest common factor is 1, so the correct answer is option (a) 1.