How many quarts of water does one add to 6 quarts of a 60% alcohol solution to create a 40% alcohol solution?

Question

a. 2qt
b. 3qt
c. 6qt
d. 9qt

Answer 1

Since you're working with water, rewrite the problem in relation to water:

X quarts of 100% water + 6 quarts of 40% water yields (x+6) quarts of 60% water.

1.00X +.40(6) = .60(6+X)
X+2.4=.6X+3.6 Isolate like terms:
.4X = 1.2 Quarts
X=3 Quarts