A tank contains 10,000 gallons of a solution that is 5 percent sodium chloride by volume. If 3,500 gallons of water evaporate from the tank, the remaining solution will be approximately what percent sodium chloride? Choose the most appropriate option
A) 6.43%  B) 6.89%  C) 7.69%  D) 8.21%  E) 8.75%
The amount of sodium chloride is 0.05*10,000 = 500 gallons   500/6500 = 1/13 which is about 7.69%   The answer is 7.69%.
<result>C</result>
A tank contains 10,000 gallons of a solution that is 5 percent sodium chloride by volume. If 3,500 gallons of water evaporate from the tank, the remaining solution will be approximately what percent sodium chloride?