HCF & LCM

JKSSB Junior Engineer (Mechanical) · Mathematics · 79 practice questions with answers and explanations: 36 Easy, 42 Medium, 1 Hard.

Sample questions

Sample Easy question 1

What is the LCM of 16 and 21?

  1. 337
  2. 672
  3. 352
  4. 336
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Answer: D. LCM(16, 21) = 336.

Sample Easy question 2

What is the LCM of 18, 15 and 9?

  1. 2430
  2. 90
  3. 108
  4. 180
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Answer: B. LCM(18, 15, 9) = 90.

Sample Easy question 3

What is the HCF of 32, 12 and 20?

  1. 4
  2. 480
  3. 8
  4. 5
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Answer: A. HCF(32, 12, 20) = 4.

Sample Medium question 4

What is the smallest number which leaves a remainder of 2 when divided by 12 as well as by 18?

  1. 74
  2. 218
  3. 36
  4. 38
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Answer: D. The required number is LCM(12, 18) + 2 = 36 + 2 = 38.

Sample Medium question 5

What is the smallest number which leaves a remainder of 3 when divided by 10 as well as by 14?

  1. 143
  2. 73
  3. 72
  4. 70
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Answer: B. The required number is LCM(10, 14) + 3 = 70 + 3 = 73.

Sample Medium question 6

What is the smallest number which leaves a remainder of 3 when divided by 8 as well as by 5?

  1. 42
  2. 40
  3. 83
  4. 43
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Answer: D. The required number is LCM(8, 5) + 3 = 40 + 3 = 43.

Sample Hard question 7

Find the HCF of the fractions 2/3, 4/9 and 8/27.

  1. 4/9
  2. 2/27
  3. 8/27
  4. 2/3
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Answer: B. HCF of fractions = HCF of numerators ÷ LCM of denominators = HCF(2, 4, 8) ÷ LCM(3, 9, 27) = 2/27.

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