if two numbers are relatively prime what is there LCM?

Answer 1

In that case it would be their product

e.g. 1/3 + 5/7
= 7/21 + 15/21
= 22/21

Answer 2

Two numbers are relatively prime when they have no prime factor in common.

If two numbers are relatively prime then their greatest common factor will be 1.

In this case:

GCF (a, b) = 1

Using the formula for product of two numbers:

a • b = GCF • LCM

a • b = 1 • LCM

a • b = LCM

LCM = a • b

Least common multiple of two relatively prime numbers is the product of those two numbers.