Precalculus (6th Edition)

Published by Pearson
ISBN 10: 013421742X
ISBN 13: 978-0-13421-742-0

Chapter 3 - Polynomial and Rational Functions - 3.6 Variation - 3.6 Exercises - Page 389: 38

Answer

$12 \ candelas$

Work Step by Step

Step 1. Assume $I\ (candelas)$ is the illumination produced by a light source. Step 2. Assume $d\ (m)$ is the distance from the source. Step 3. From the given conditions, we have $I=k/d^2$ and $70=k/(5)^2$, thus $k=1750$ Step 4. For $d=12\ (m)$, we have $I=1750/(12)^2\approx12.153\approx12\ candelas$
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