a watch was sold at a loss of 10 % . if it was sold for rs . 180 more , there would have been a gain of 5 % . what is the cost price ?
"90 % 105 % - - - - - - - - 15 % - - - - 180 100 % - - - - ? = > rs . 1200 answer : a"
divide(multiply(180, const_100), subtract(add(const_100, 5), subtract(const_100, 10)))