What is the least common multiple for 21 and 35?

Answer 1

Expressing each number as the product of prime numbers can help a lot:

21 = 3x7

35 = 5x7

7 is the greatest common factor(H.C.F.) of 21 and 35.

H.C.F.(21,35) = 7

Method to find L.C.M. of x and y:

L.C.M.(x,y) = H.C.F.(x,y) x Product of other no. in prime factorizations of x and y

So, L.C.M.(21,35) = H.C.F.(21,35) x 3x5 = 7x3x5 = 21x5 = 105.