How can you find the multiples of two denominators?

Answer 1

Example: 1/30 and 1/42

Factor them.

2 x 3 x 5 = 30

2 x 3 x 7 = 42

Select the highest amount of each factor.

2 x 3 x 5 x 7 = 210, the LCD

Answer 2

They are members of infinite sets of the form k*D where D is the denominator and k is any integer.

Answer 3

It is a common denominator: useful for adding or subtracting fractions.

Answer 4

That's a common denominator.