If the cost price of 140 pencils is equal to the selling price of 100 pencils, the gain percent is  Select the correct option.
A) 36
B) 37
C) 38
D) 39
E) 40

Rationale: "let c . p . of each pencil be re . 1 . then , c . p . of 100 pencils = rs . 100 ; s . p . of 100 pencils = rs . 140 . gain % = 40 / 100 * 100 = 40 % answer : e"
Answer: E