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Activity Discussion Math How to find LCM and HCF? Reply To: How to find LCM and HCF?

  • Jyothi krishna

    May 12, 2021 at 11:46 am
    Not Helpful

    Highest Common Factor (H.C.F) : It is also called

    Greatest common Diviser (G.C.D). When a greatest number

    divides perfectly the two or more given numbers then that

    number is called the H.C.F. of two or more given numbers.


    The H.C.F of 10, 20, 30 is 10 as they are perfectly

    divided by 10,5 and 2 and 10 is highest or greatest of


    Least common Multiple (L.C.M.) : The least number

    which is divisible by two or more given numbers, that least

    number is called L.C.M. of the numbers.

    L.C.M. of 3,5,6 is 30, because all 3 numbers divide

    30, 60, 90, …… and so on perfectly and 30 is minimum of


    Factor and Multiple : If a number m, divides perfectly

    second number n, then m is called the factor of n and n is

    called the multiple of m.

    Rule 1 : 1st number × 2nd number = L.C. M. × H.C.F.

    l There are two methods for calculating the H.C.F

    and L.C.M.

    (i) Factor Method

    (ii) Division Method

    l If the ratio of two numbers is a:b, (lowest form i.e.

    indivisible to each other) then

    Numbers are ak and bk, where k is a constant and


    H.C.F. is K and L.C.M. is abk

    Rule 2 :

    L.C.M of fractions=L.C.M.of numerators/

    H.C.F.of denominators

    Rule 3 :

    H.C.F. of fractions=H.C.F of numerators/

    L.C.M.of denominators

    l If there is no common factor between two numbers,

    then L.C.M. will be the product of both numbers.

    l If there are ‘n’ numbers in a set and H.C.F. of any two

    numbers is H and L.C.M. of all ‘n’ numbers is L, then

    product of all ‘n’ numbers is [(H)^n-1×L].

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