if the selling price of 50 articles is equal to the cost price of 30 articles , then the loss or gain percent is :
"let c . p . of each article be re . 1 . then , c . p . of 50 articles = rs . 50 ; s . p . of 50 articles = rs . 30 . loss % = 20 / 50 * 100 = 40 % answer : b"
subtract(const_100.0, 30)