In order to add or subtract fractions, they must have the same denominator. And the Least Common Denominator (LCD) for a set of fractions is the least common multiple (LCM) of their denominator.

Example 1: Would you like to know what the Least Common Denominator of 1/2, 1/9, 1/6 is?

Solution 1: The LCD of 1/2, 1/9, 1/6 = 2 x 3 x 3 = 18

Would you like to try a simple exercise?

Exercise: What is the Least Common Multiple of 1/5, 1/7, 1/8, 1/9?

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Example 2: Would you like to know what the Least Common Denominator of 1/3, 1/5, 1/6, 1/9 is?

Solution 2: The LCD of 1/3, 1/5, 1/6, 1/9 = 3 x 5 x 2 x 3 = 90

Would you like to try another exercise?

Exercise: What is the Least Common Multiple of 1/9, 1/18, 1/100, 1/30?