Elementary Algebra

Published by Cengage Learning
ISBN 10: 1285194055
ISBN 13: 978-1-28519-405-9

Chapter 4 - Proportions, Percents, and Solving Inequalities - 4.5 - Inequalities, Compound Inequalities, and Problem Solving - Problem Set 4.5: 72

Answer

She needs to have a score equal to or higher than 98 to achieve an average of 85 or higher for the four tests.

Work Step by Step

Let x represent the score of the fourth test. Her average will be $\frac{87+81+74+x}{4}$. Because she needs to have an average of 85 or higher for the four tests, we solve the following inequality. $\frac{87+81+74+x}{4}$ $\geq$ 85 Multiply both sides by 4. 87+81+74+x $\geq$ 340 x + 242 $\geq$ 340 x $\geq$ 98 As we can see, she needs to have a score equal to or higher than 98 to achieve an average of 85 or higher for the four tests.
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