how many liters of water must be evaporated from 50 liters of a 2 - percent sugar solution to get a 10 - percent solution ?
"2 % of a 50 liter solution is 1 l which is 10 % of the solution at the end . the solution at the end must be 1 l . we need to evaporate 40 liters . the answer is d ."
subtract(50, multiply(divide(50, const_100), 10))