If the cost price of 55 articles is equal to the selling price of 50 articles, then what is the percent profit?	Choices.
A) 5 %
B) 10 %
C) 15 %
D) 20 %
E) 25 %

Rationale: "let x be the cost price of one article . let y be the selling price of one article . 50 y = 55 x y = 1.1 x the answer is b ."
Answer: B