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Least Common Denominator

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Finding a least common denominator (LCD), a selection of answers from the Dr. Math archives.

We can't add or subtract fractions unless they have a common denominator.

The least common denominator of two fractions is the least common multiple of the denominators of those fractions. Here are several methods from the Dr. Math archives for finding the LCD:

Finding Least Common Denominator
Three different methods.

Denominators
I have a problem with different denominators... 4/5+5/6+7/16 = ? What is the best and fastest way to find the LCD?

Finding LCDs, LCMs, and GCFs
How do you find the greatest common factor, the least common multiple, and the least common denominator?

LCD, LCM
What is the easiest way to find the least common denominator and least common multiple of two numbers?

Least Common Multiple
I need to find the LCM of the numbers 16, 20, 9, and 8.

And see: Prime Factoring.

Return to
Elementary Fractions and Decimals
Middle School Fractions and Percentages
Middle School Factoring Numbers
Index of Selected Answers to Common Questions

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