The ratio of the number of men to the number of women in a 20 member committee is 3:1. How many women must be added to the 20member committee so as to make the ratio of men to women 3:2?

A.
2 
B.
5 
C.
7 
D.
9
Correct Answer: Option B
Explanation
20 members in the ratio 3:1
Number of women = (frac{1}{4} times 20)
= 5
Let the number of women to be added = x
Total number of members in the committee = 20 + x
(frac{5 + x}{20 + x} = frac{2}{5})
(5(5 + x) = 2(20 + x))
(25 + 5x = 40 + 2x implies 5x – 2x = 40 – 25)
(3x = 15 implies x = 5)