boy sells a book for rs . 810 he gets a loss of 10 % , to gain 10 % , what should be the sp ?
"cost price = 810 / 90 x 100 = 900 to gain 10 % = 900 x 10 / 100 = 90 sp = cp + gain = 900 + 90 = 990 answer : b"
add(divide(810, subtract(const_1, divide(10, const_100))), multiply(divide(810, subtract(const_1, divide(10, const_100))), divide(10, const_100)))