A chemist mixes one liter of pure water with x liters of a 50% salt solution, and the resulting mixture is a 10% salt solution. What is the value of x?  Choose the correct choice:
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 = 50 % concentration of salt in the mixed solution = 10 % the pure solution and the salt solution is mixed in the ratio of - - > ( 50 - 10 ) / ( 10 - 0 ) = 4 / 1 1 / x = 4 / 1 x = 1 / 4 answer : a
Answer: A