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 ?
"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 ."
subtract(90, multiply(divide(90, const_100), 10))