A shirt goes on sale for 90% of its original price. One week later, the sale price is marked down 10%. The final price is what percent of the original price?	Choices.
A) 72 %
B) 81 %
C) 52 %
D) 50 %
E) 28 %

Rationale: "just assume original price is 100 . sale price = 90 then it is marked down by 10 % = 90 - 9 = 81 . hence it is 81 % od the original price . hence answer is b ."
Answer: B