5 men and 2 boys together in 1 hour do 4 times work as 1 man and 1 boy do in an hour. Determine the ratio of the efficiency of a man and a boy.

A 4 : 1

B 1 : 4

C 3 : 4

D 2 : 1

E 1 : 2

Correct Answer: Option D

Let Work done by 1 man in 1 hour be M units.

Also, let the work done by 1 boy in 1 hour be B units

∴ Work done by 1 man and one boy in 1 hour = M + B

∴ Work done by 5 men and 2 boys in one hour = 5M + 2B

Now, as per the given information,

5M + 2B = 4 × (M + B)

5M + 2B = 4M + 4B

M = 2B

M : B = 2 : 1

∴ratio of efficiency = M : B = 2 : 1