by selling 16 pencils for a rupee a man loses 10 % . how many for a rupee should he sell in order to gain 20 % ?
"90 % - - - 16 120 % - - - ? 90 / 120 * 16 = 12 answer : c"
multiply(divide(const_1, multiply(add(const_100, 20), divide(const_1, subtract(const_100, 10)))), 16)