There is a group of 5 boys and 2 girls. The two groups working together can do four times as much work as a boy and a girl. Ratio of working capacities of a boy and a girl is:

Answer: Option A

Let 1 boy's 1 day's work = x
And 1 girl's 1 day's work = y
Now,
(5 boys + 2 girls)'s work = 5x + 2y
Given ,
5x + 2y is equal to 4 times work done by a boy and a girl
Thus,
5x + 2y = 4(x + y)
5x + 2y = 4x + 4y
x = 2y
$$\frac{\text{x}}{\text{y}}=\frac{2}{1}$$
Hence, the required ratio is 2 : 1