Intermediate Algebra for College Students (7th Edition)

Published by Pearson
ISBN 10: 0-13417-894-7
ISBN 13: 978-0-13417-894-3

Chapter 4 - Section 4.1 - Solving Linear Inequalities - Exercise Set - Page 264: 60

Answer

More than $300$ calling minutes in a month make plan A the better deal.

Work Step by Step

Let the number of calling minutes in a month be $x$. Plan A monthly fees equal $\$15$ plus $\$0.08$ per minute. Plan B monthly fees equal $\$3$ plus $\$0.12$ per minute. In the mathematical form. Plan A monthly fees $=15+0.08x$. Plan B monthly fees $=3+0.12x$. For plan A to be the better deal the inequality is. Plan B monthly fees $>$ Plan A monthly fees. The inequality is $\Rightarrow 3+0.12x>15+0.08x$. Add $-3-0.08x$ to both sides. $\Rightarrow 3+0.12x-3-0.08x>15+0.08x-3-0.08x$. Simplify. $\Rightarrow 0.04x>12$. Divide both sides by $0.04$. $\Rightarrow \frac{0.04x}{0.04}>\frac{12}{0.04}$. Simplify. $\Rightarrow x>300$. Hence, more than $300$ calling minutes in a month make plan A the better deal.
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