Elementary Algebra

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

Chapter 7 - Algebraic Fractions - 7.6 - More Fractional Equations and Problem Solving - Problem Set 7.6 - Page 315: 40


She walked at 4 mph and jogged at 8 mph

Work Step by Step

We first find her average velocity: $v = 20/4 = 5$ mph We call j the jogging rate and w the walking rate. Recall, she jogs 40 percent of the time and walks 60 percent of the distance. Since her jogging rate is twice her walking rate, this means she jogs 25 percent of the time and walks 75 percent of the time. Thus: $.25j + .75w = 5 \\ .25(2w) + .75w = 5 \\ w =4$ Since she jogs twice as fast, this means she jogs at 8 mph.
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