Problem: the cost price of an article is 64 % of the marked price . calculate the gain percent after allowing a discount of 20 % ?
Rationale: "explanation : let marked price = rs . 100 . then , c . p . = rs . 64 , s . p . = rs . 80 gain % = 16 / 64 * 100 = 25 % . answer : option e"
annotated_formula: multiply(subtract(divide(subtract(const_100, 20), 64), const_1), const_100)