What is the Least Common Multiple of 28 and 42?
Least common multiple or lowest common denominator (lcd) can be calculated in two way; with the LCM formula calculation of greatest common factor (GCF), or multiplying the prime factors with the highest exponent factor.
Least common multiple (LCM) of 28 and 42 is 84.
LCM(28,42) = 84
Least Common Multiple of 28 and 42 with GCF Formula
The formula of LCM is LCM(a,b) = ( a × b) / GCF(a,b).
We need to calculate greatest common factor 28 and 42, than apply into the LCM equation.
GCF(28,42) = 14
LCM(28,42) = ( 28 × 42) / 14
LCM(28,42) = 1176 / 14
LCM(28,42) = 84
Least Common Multiple (LCM) of 28 and 42 with Primes
Least common multiple can be found by multiplying the highest exponent prime factors of 28 and 42. First we will calculate the prime factors of 28 and 42.
Prime Factorization of 28
Prime factors of 28 are 2, 7. Prime factorization of 28 in exponential form is:
28 = 22 × 71
Prime Factorization of 42
Prime factors of 42 are 2, 3, 7. Prime factorization of 42 in exponential form is:
42 = 21 × 31 × 71
Now multiplying the highest exponent prime factors to calculate the LCM of 28 and 42.
LCM(28,42) = 22 × 71 × 31
LCM(28,42) = 84