College Algebra 7th Edition

Published by Brooks Cole
ISBN 10: 1305115546
ISBN 13: 978-1-30511-554-5

Chapter 1, Equations and Graphs - Section 1.10 - Modeling Variation - 1.10 Exercises - Page 164: 4



Work Step by Step

If $z$ is directly proportional to the product of $x$ and $y$ and if $z$ is 10 when $x$ is 4 and $y$ is 5, then $x$, $y$, and $z$ are related by the equation ___$z =\frac{1}{2}xy$___. We know this because $z$ is jointly proportionaI to $x$ and $y$. So the general equation must be: $z=kxy$. To solve for $k$, we substitute the given values: $10=k*4*5$ $10=20k$ $k=\frac{1}{2}$
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