Problem: if the selling price of 80 articles is equal to the cost price of 40 articles , then the loss or gain percent is :
Rationale: "let c . p . of each article be re . 1 . then , c . p . of 80 articles = rs . 80 ; s . p . of 80 articles = rs . 40 . loss % = 40 / 80 * 100 = 50 % answer : c"
annotated_formula: subtract(80, 40)