HCF & LCM

LSSSSB Non-Technical · 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 24, 6 and 5?

  1. 120
  2. 144
  3. 240
  4. 720
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Answer: A. LCM(24, 6, 5) = 120.

Sample Easy question 2

What is the HCF of 18, 6 and 21?

  1. 6
  2. 4
  3. 126
  4. 3
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Answer: D. HCF(18, 6, 21) = 3.

Sample Easy question 3

Three bells ring together at 8:00 a.m. and then ring at intervals of 9, 8 and 12 minutes. After how many minutes will they next ring together?

  1. 29
  2. 144
  3. 36
  4. 72
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Answer: D. The next common ring is after LCM(9, 8, 12) = 72 minutes.

Sample Medium question 4

What is the LCM of 24, 15 and 3?

  1. 240
  2. 120
  3. 1080
  4. 144
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Answer: B. LCM(24, 15, 3) = 120.

Sample Medium question 5

What is the HCF of 15, 50 and 45?

  1. 5
  2. 450
  3. 6
  4. 10
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Answer: A. HCF(15, 50, 45) = 5.

Sample Medium question 6

The HCF of two numbers is 4 and their LCM is 40. If one number is 20, what is the other?

  1. 20
  2. 12
  3. 60
  4. 8
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Answer: D. Product of the numbers = HCF × LCM, so other = 4×40/20 = 8.

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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