A dishonest dealer professes to sell goods at the cost price but uses a weight of 780 grams per kg, what is his percent? Choose the correct answer
A) 28 % B) 25 % C) 55 % D) 28 % E) 28.2 %

Rationale: "780 - - - 220 100 - - - ? = > 28.2 % answer : e"
Answer: E