If 3 gallons of spirit containing 20% water are added to 5 gallons of another spirit containing 15% water, what percentage of the mixture is water?

A.
2(frac{4}{5})% 
B.
16(frac{7}{8})% 
C.
18(frac{1}{8})% 
D.
18(frac{7}{8})%
Correct Answer: Option B
Explanation
% of water in the mixture
= (frac{text{Total Amount of water}}{text{Total quantity of spirit}}) x (frac{100}{1})
(frac{3(frac{20}{100}) + 5 (frac{15}{100})}{3 + 5}) x (frac{100}{1})
= (frac{frac{6}{10} + frac{75}{100}}{8}) x (frac{100}{1})
= (frac{0.6 + 0.75}{8}) x (frac{100}{1})
= (frac{1.35}{8}) x (frac{100}{1})
= (frac{33.75}{2})
= 16.875
= 16(frac{7}{8})