Elementary Algebra

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

Chapter 3 - Equations and Problem Solving - Chapter 3 Review Problem Set - Page 138: 46


20 liters of alcohol must be added.

Work Step by Step

Let X represent the amount of pure alcohol to be added. The second solutions is 10 liters. The resulting solution will be 10 + X liters. We use the following guideline to solve this problem: Amount of alcohol in the first solution + amount of alcohol in the second solution = Amount of alcohol in the final solution. The first solution is all alcohol; it has X liters of it. The second solution has 10 $\times$ 70% = 10 $\times$ 0.7 = 7 liters of alcohol. The resulting solutions is 90% alcohol, which means it has 90% $\times$ (10+X) = 0.9 $\times$ (10 + X) = 9 + 0.9X alcohol. We then solve the equation: X + 7 = 9 + 0.9X 0.1X = 2 Divide both sides by 0.1 X = 20 20 liters of alcohol must be added.
Update this answer!

You can help us out by revising, improving and updating this answer.

Update this answer

After you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.