Elementary Algebra

Published by Cengage Learning
ISBN 10: 1285194055
ISBN 13: 978-1-28519-405-9

Chapter 2 - Real Numbers - 2.2 - Addition and Subtraction of Rational Numbers - Concept Quiz 2.2 - Page 57: 7



Work Step by Step

When finding a common denominator, we may use any number that is a multiple of the denominators of all of the fractional addends. Since $20$, $40$, and $60$ are all multiples of both $4$ and $5$, any of them can be used as a common denominator. Since $20$ is the $\text{least}$ common multiple of $4$ and $5$, it is the $\text{least}$ common denominator.
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