by selling 20 pencils for a rupee a man loses 30 % . how many for a rupee should he sell in order to gain 30 % ?
"70 % - - - 20 130 % - - - ? 70 / 130 * 20 = 10.75 answer : b"
multiply(divide(const_1, multiply(add(const_100, 30), divide(const_1, subtract(const_100, 30)))), 20)