By selling an article for $180, a person gains $30. What is the gain %?
Pick one:
A) 25 %
B) 30 %
C) 50 %
D) 20 %
E) 10 %

Rationale: "s . p . = $ 180 gain = $ 30 c . p . = 180 - 30 = 150 gain % = 30 / 150 * 100 = 20 % answer is d"
Answer: D