Algebra 1

Published by Prentice Hall
ISBN 10: 0133500403
ISBN 13: 978-0-13350-040-0

Chapter 10 - Radical Expressions and Equations - 10-4 Solving Radical Equations - Practice and Problem-Solving Exercises - Page 624: 38


approximately $511,185,933$ $km^2$

Work Step by Step

Using the given formula, $ r=\sqrt{\dfrac{A}{4\pi}} ,$ with $ r=6378$ $km$, then \begin{array}{l}\require{cancel} 6378=\sqrt{\dfrac{A}{4\pi}} \\\\ (6378)^2=\left(\sqrt{\dfrac{A}{4\pi}}\right)^2 \Rightarrow\text{ (square both sides)} \\\\ 40678884=\dfrac{A}{4\pi} \\\\ 4\pi\cdot40678884=\dfrac{A}{4\pi}\cdot4\pi \\\\ 162715536\pi=A \\\\ A=162,715,536\pi \\\\ A\approx511,185,933 .\end{array} Hence, the surface area, $A,$ of the earth is approximately $511,185,933$ $km^2$.
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