Question

How many quarts of a 50% solution of acid must be added to 20 quarts of a 20% solution of acid to obtain a mixture containing a 40% solution of acid?

Answer 1

40

Explanation:

Answer 2

suppose x quarts of the 50% solution
0.5x+0.2*20=0.4(x+20)
0.5x+4=0.4x+8
0.1x=4
x=40