Some of 50%-intensity red paint is replaced with 20% solution of red paint such that the new paint intensity is 40%. What fraction of the original paint was replaced?	Pick one.
A) 1 / 3  B) 1 / 5  C) 2 / 3  D) 3 / 4  E) 4 / 5

Rationale: "40 % is 20 % - points above 20 % and 10 % - points below 50 % . thus the ratio of 20 % - solution to 50 % - solution is 1 : 2 . 1 / 3 of the original paint was replaced . the answer is a ."
Answer: A