A shopkeeper sold an article at $100 with 10% profit. Then find its cost price?	Choose one:
A) $ 120
B) $ 100
C) $ 91
D) $ 72
E) $ 69

Rationale: "cost price = selling price * 100 / ( 100 + profit ) c . p . = 100 * 100 / 110 = $ 91 ( approximately ) answer is c"
Answer: C