Problem: how many liters of water must be evaporated from 50 liters of a 6 - percent sugar solution to get a 10 - percent solution ?
Rationale: "6 % of a 50 liter solution is 3 l which is 10 % of the solution at the end . the solution at the end must be 30 l . we need to evaporate 20 liters . the answer is a ."
annotated_formula: subtract(50, multiply(divide(50, const_100), 10))