The ratio between the sale price and the cost price of an article is 10:7. What is the ratio between the profit and the cost price of that article?	Choose the correct answer.
A) 2 : 9  B) 2 : 5  C) 3 : 7  D) 2 : 0  E) 2 : 1

Rationale: "let c . p . = rs . 7 x and s . p . = rs . 10 x . then , gain = rs . 3 x required ratio = 3 x : 7 x = 3 : 7 answer : c"
Answer: C