Intermediate Algebra (6th Edition)

Published by Pearson
ISBN 10: 0321785045
ISBN 13: 978-0-32178-504-6

Chapter 6 - Section 6.7 - Variation and Problem Solving - Exercise Set - Page 397: 7


$k=.25$, $y=.25x$

Work Step by Step

If y varies directly as x, we know that the variables x and y can be related by the function $y=kx$, where k is the constant of proportionality. If $y=.2$ when $x=.8$, then we know that $.2=.8k$ (or $\frac{1}{5}=\frac{4}{5}k$). Multiply both sides by 5. $4k=1$ Divide both sides by 4. $k=\frac{1}{4}=.25$ Therefore, the constant of variation is $k=.25$ and the direct variation equation is $y=.25x$.
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