A pot filled with 1 kilogram of solution contains 7 percent sodium chloride by weight in water. if water is boiled off

[M7MBA]

A pot filled with 1 kilogram of solution contains 7 percent sodium chloride by weight in water. if water is boiled off until the amount of solution has decreased by 30 percent, the remaining solution will be approximately what percent sodium chloride by weight?

a) 4.28%
b) 7%
c) 10%
d) 21%
e) 90%

[spoiler]OA=C[/spoiler]

Source: Veritas Prep

[Scott@TargetTestPrep]

A pot filled with 1 kilogram of solution contains 7 percent sodium chloride by weight in water. if water is boiled off until the amount of solution has decreased by 30 percent, the remaining solution will be approximately what percent sodium chloride by weight?

a) 4.28%
b) 7%
c) 10%
d) 21%
e) 90%

[spoiler]OA=C[/spoiler]

Instead of 1 kg of solution, let’s use 100 kg (since the answer would be the same as long as we maintain the same proportion). So initially we have 7 kg of sodium chloride and 93 kg of water. After 30% of the solution is evaporated (notice that only water evaporates), we have 70 kg of solution, of which 7 kg is still sodium and 63 kg is water. Therefore, sodium chloride is 7/70 = 1/10 = 10% of the remaining solution.

Answer: C