A chemist mixes one liter of pure water with x liters of a 40% salt solution, and the resulting mixture is a 20% salt solution. What is the value of x?  Select
A) 1 / 4  B) 1 / 3  C) 1 / 2  D) 1  E) 3

Rationale: "concentration of salt in pure solution = 0 concentration of salt in salt solution = 40 % concentration of salt in the mixed solution = 20 % the pure solution and the salt solution is mixed in the ratio of - - > ( 40 - 20 ) / ( 20 - 0 ) = 1 / 1 1 / x = 1 / 1 x = 1 answer : d"
Answer: D