the tax on a commodity is diminished by 20 % but its consumption is increased by 20 % . find the decrease percent in the revenue derived from it ?
"100 * 100 = 10000 80 * 120 = 9600 10000 - - - - - - - 400 100 - - - - - - - ? = 4 % answer : c"
subtract(const_100, divide(multiply(add(const_100, 20), subtract(const_100, 20)), const_100))