The proportion of water to alcohol in Solution A is 4:1 and the proportion of water to alcohol in Solution B is 3:1. If an equal amount of each solution is mixed together, what is the concentration of alcohol in the new solution?  Choose one
A) 16.5 %	B) 18.5 %	C) 20.5 %	D) 22.5 %	E) 24.5 %

Rationale: "let v be the total volume of the new solution . then a volume of v / 2 was added from each solution a and b . the amount of alcohol added to the new solution was : ( 1 / 5 ) ( v / 2 ) + ( 1 / 4 ) ( v / 2 ) = v / 10 + v / 8 = 9 v / 40 . the concentration of alcohol is 9 / 40 = 22.5 % the answer is d ."
Answer: D