Problem: a man buys an article for $ 100 . and sells it for $ 125 . find the gain percent ?
Rationale: "c . p . = $ 100 s . p . = $ 125 gain = $ 25 gain % = 25 / 100 * 100 = 25 % answer is c"
annotated_formula: subtract(divide(125, divide(100, const_100)), const_100)