Question

One thousand liters of a solution was available, but the solution was 90% alcohol. Jim needed a solution that was 80% alcohol. How many liters of the solution needed to be extracted so the solution was 80% alcohol?

Answer 1

(1000(90%) - x(100%))/(1000 - x) = 80%
1000(0.9) - x(1.0) = (1000 - x)(0.8)
900 - x = 800 - 0.8x
100 = 0.2x
500 = x
500 liters of pure alcohol had to be taken out.