LCM and HCF: Test 1

10 questions · 15 minutes · scoring and calculator rules shown before you begin

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LCM and HCF Test 1: questions and answers

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  1. 1. Find the LCM of 8, 10, 12.
    1. 2
    2. 120
    3. 180
    4. 960

    Reference: q-8b0ca6b4-27 · Report this question

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    Answer: B. 120

    LCM of 8, 10, 12 = 120, the smallest number divisible by all three.
  2. 2. Find the HCF of 55 and 99.
    1. 495
    2. 11
    3. 9
    4. 10

    Reference: q-ffa7d51a-27 · Report this question

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    Answer: B. 11

    55 = 11 × 5 and 99 = 11 × 9, where 5 and 9 have no common factor. HCF = 11.
  3. 3. The HCF and LCM of two numbers are 9 and 54. If one of the numbers is 18, find the other.
    1. 27
    2. 45
    3. 54
    4. 6

    Reference: q-b7259ec6-90 · Report this question

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    Answer: A. 27

    Product of the numbers = HCF × LCM. Other number = 9 × 54 / 18 = 27.
  4. 4. Three bells ring at intervals of 4, 10 and 12 seconds. If they ring together now, after how many seconds will they next ring together?
    1. 50 seconds
    2. 26 seconds
    3. 60 seconds
    4. 80 seconds

    Reference: q-4c9d419e-135 · Report this question

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    Answer: C. 60 seconds

    They ring together again after the LCM of 4, 10, 12, which is 60 seconds.
  5. 5. Find the least number which when divided by 15, 20, 30 leaves a remainder of 9 in each case.
    1. 72
    2. 51
    3. 60
    4. 69

    Reference: q-d57922d5-93 · Report this question

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    Answer: D. 69

    LCM of 15, 20, 30 = 60. Required number = 60 + 9 = 69.
  6. 6. Find the greatest number that divides 103 and 53 leaving remainders 3 and 13 respectively.
    1. 20
    2. 17
    3. 23
    4. 21

    Reference: q-27e2314c-91 · Report this question

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    Answer: A. 20

    Required number = HCF of (103 − 3) and (53 − 13) = HCF of 100 and 40 = 20.
  7. 7. Find the LCM of 16, 24, 32.
    1. 80
    2. 8
    3. 96
    4. 12,288

    Reference: q-27dfcf5a-28 · Report this question

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    Answer: C. 96

    LCM of 16, 24, 32 = 96, the smallest number divisible by all three.
  8. 8. Find the HCF of 120 and 45.
    1. 360
    2. 12
    3. 15
    4. 13

    Reference: q-5e071170-28 · Report this question

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    Answer: C. 15

    120 = 15 × 8 and 45 = 15 × 3, where 8 and 3 have no common factor. HCF = 15.
  9. 9. The HCF and LCM of two numbers are 10 and 140. If one of the numbers is 70, find the other.
    1. 20
    2. 14
    3. 30
    4. 10

    Reference: q-1c9d1830-92 · Report this question

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    Answer: A. 20

    Product of the numbers = HCF × LCM. Other number = 10 × 140 / 70 = 20.
  10. 10. Three bells ring at intervals of 15, 20 and 30 seconds. If they ring together now, after how many seconds will they next ring together?
    1. 80 seconds
    2. 65 seconds
    3. 30 seconds
    4. 60 seconds

    Reference: q-52b5fa29-136 · Report this question

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    Answer: D. 60 seconds

    They ring together again after the LCM of 15, 20, 30, which is 60 seconds.

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