Question

137. A man and a boy can do a piece of work in
36 days. If the man works alone for the last
10 days, it is completed in 40 days. How long
would the boy take to do it alone?
(A) 85 days
(B) 100 days
(C) 80 days
(D) 90 days​

Answer 1

Answer:

Step-by-step explanation:

(M+B)24 is Total Work.

=> (M+B)24 = (M+B)20 + (M)6

[Because now total work is completed in 26 days (Man alone does the work for last 6 days, therefore remaining work done by M+B for 20 days).]

By solving above equation:

=> M/B = 2/1 (Efficiency of M and B)

The boy will take to complete the work alone:

=> (M+B)24 = (B)D

=> (2+1)24 = (1)D

=> D = 72