Problem: a pair of articles was bought for $ 1000 at a discount of 10 % . what must be the marked price of each of the article ?
Rationale: "s . p . of each of the article = 1000 / 2 = $ 500 let m . p = $ x 90 % of x = 500 x = 500 * 100 / 90 = $ 555.55 answer is a"
annotated_formula: divide(multiply(subtract(const_100, 10), divide(1000, const_2)), const_100)