LCM and HCF


  1. How many numbers are there between 4000 and 6000 which are exactly divisible by 32, 40, 48 and 60?









  1. View Hint View Answer Discuss in Forum

    LCM of 32, 40, 48 and 60 = 480
    The number divisible by 480 between 4000 and 6000 are 4320, 4800, 5280 and 5760.

    Correct Option: C

    LCM of 32, 40, 48 and 60 = 480
    The number divisible by 480 between 4000 and 6000 are 4320, 4800, 5280 and 5760.

    Hence, required number of numbers are 4.


  1. The sum of two numbers is 1056 and their HCF is 66, Find the Number of such pairs.











  1. View Hint View Answer Discuss in Forum

    Let the numbers be 66a and 66b, where a and b are co-primes.

    According to the question,
    66a + 66b = 1056
    ⇒ 66(a + b) = 1056
    ⇒ (a + b) = 1056/66 = 16
    ∴ Possible values of a and b are
    (a = 1, b = 15), (a = 3, b = 13).
    (a = 5, b = 11 ), (a = 7, b = 9)

    Correct Option: C

    Let the numbers be 66a and 66b, where a and b are co-primes.

    According to the question,
    66a + 66b = 1056
    ⇒ 66(a + b) = 1056
    ⇒ (a + b) = 1056/66 = 16
    ∴ Possible values of a and b are
    (a = 1, b = 15), (a = 3, b = 13).
    (a = 5, b = 11 ), (a = 7, b = 9)
    ∴ Numbers are
    (66 x 1, 66 x 15), (66 x 3, 66 x 13),
    (66 x 5, 66 x 11), (66 x 7, 66 x 9).
    ∴ Possible number of pairs = 4



  1. The HCF and LCM of two natural numbers are 12 and 72, respectively. What is the difference between the two numbers, if one of the number is 24?









  1. View Hint View Answer Discuss in Forum

    Second number = (LCM x HCF) / first number

    Correct Option: A

    Second number = (LCM x HCF) / first number
    = (72 x 12)/ 24 = 36
    Difference between the two numbers
    = 36 - 24 = 12


  1. The ratio of two numbers is 3 : 4 and their HCF is 4. What will be their LCM?











  1. View Hint View Answer Discuss in Forum

    According to the question,
    1st number = 3M, 2nd number = 4M
    where, M = HCF

    But given, M = 4
    We know that,
    LCM = Product of two numbers / HCF

    Correct Option: D

    According to the question,
    1st number = 3M, 2nd number = 4M
    where, M = HCF

    But given, M = 4
    We know that,
    LCM = Product of two numbers / HCF
    = (3M x 4M) / M
    LCM = 12M = 12 x 4 = 48



  1. For any integer n, What is HCF (22n + 7, 33n + 10) equal to?









  1. View Hint View Answer Discuss in Forum

    HCF of (22n + 7, 33n + 10) is always 1.
    lllustraction
    For n = 1, HCF(29, 43) ⇒ HCF = 1
    For n = 2, HCF(51, 76) ⇒ HCF = 1
    For n = 3, HCF(73, 109) ⇒ HCF = 1

    Correct Option: B

    HCF of (22n + 7, 33n + 10) is always 1.
    lllustraction
    For n = 1, HCF(29, 43) ⇒ HCF = 1
    For n = 2, HCF(51, 76) ⇒ HCF = 1
    For n = 3, HCF(73, 109) ⇒ HCF = 1