In the lab, Ravi has two solutions that contain alcohol

Question

In the lab, Ravi has two solutions that contain alcohol and is mixing them with each other. He uses 3

 times as much Solution A as Solution B. Solution A is  20%

alcohol and Solution B is  13%

 alcohol. How many milliliters of Solution B does he use, if the resulting mixture has 292

 milliliters of pure alcohol? 

Answer 1

Let a = # of milliliters of the 20% solution

Let b = # of milliliters of the 13% solution

Note that a = 3b (given)

(a(20) + b(13))/(20 + 30) = 292 or (3b(20) + b(13))/(20 + 30) = 292

Solving, 73b = 9636 or b = 132 ml