How do you get common denominators?

Answer 1

Find the LCM of the denominators.

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 Least Common Denominator.

1/30 = 7/210

1/42 = 5/210