Elementary and Intermediate Algebra: Concepts & Applications (6th Edition)

Published by Pearson
ISBN 10: 0-32184-874-8
ISBN 13: 978-0-32184-874-1

Chapter 6 - Rational Expressions and Equations - Review Exercises: Chapter 6 - Page 438: 43


$$ \frac{36}{7}{hours}$$

Work Step by Step

We add the rates to find their combined rate: $$ \frac{1}{9}+\frac{1}{12}\\ \frac{4}{36}+\frac{3}{36}\\ \frac{7}{36}$$ Thus, taking the reciprocal, their combined time is: $$ \frac{36}{7}{hours}$$
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