by selling 8 pencils for a rupee a man loses 10 % . how many for a rupee should he sell in order to gain 10 % ?
"90 % - - - 8 110 % - - - ? 90 / 110 * 8 = 6.54 answer : a"
multiply(divide(const_1, multiply(add(const_100, 10), divide(const_1, subtract(const_100, 10)))), 8)