Some of 50%-intensity red paint is replaced with 20% solution of red paint such that the new paint intensity is 30%. What fraction of the original paint was replaced?	Options
A) 1 / 30 B) 1 / 5 C) 2 / 3 D) 3 / 4 E) 4 / 5

Rationale: 30 % is 10 % - points above 20 % and 20 % - points below 50 % . thus the ratio of 25 % - solution to 50 % - solution is 2 : 1 . 2 / 3 of the original paint was replaced . the answer is c .
Answer: C