If 4 boys and 6 girls can do a work in 8 days, and 3 boys and 7 girls can finish the same in 10 days, find the ratio of capacities of a boy and a girl.

Correct option is C

Let efficiency of 1 boy and 1 girl be x and y.
According to the question
(4x+6y) x 8 = (3x + 7y) x 10
32x+48y = 30x + 70y
32x-30x = 70y - 48y
=> 2x= 22y
=>x:y = 11:1
Efficiency ratio, x: y = 11: 1.