1/30 + 1/40 = 7/120
120/7 = 17 1/7 days
This justifies what answer for what question? Q & A: 
Ravi can do a piece of work in 30 days while Prakash can do it in 40 days. In how many days will they finish it together?
Options:
(A) 17 1/7 days
(B) 27 1/7 days
(C) 23 2/7 days
(D) 16 4/11 days
(E) none of these
(A)
1/30 + 1/40 = 7/120
120/7 = 17 1/7 days
This justifies what answer for what question? Q & A: 
user
Ravi can do a piece of work in 30 days while Prakash can do it in 40 days. In how many days will they finish it together?
Options:
(A) 17 1/7 days
(B) 27 1/7 days
(C) 23 2/7 days
(D) 16 4/11 days
(E) none of these
(A)
assistant
1/30 + 1/40 = 7/120
120/7 = 17 1/7 days
This justifies what answer for what question? Q & A: 
Ravi can do a piece of work in 30 days while Prakash can do it in 40 days. In how many days will they finish it together?
Options:
(A) 17 1/7 days
(B) 27 1/7 days
(C) 23 2/7 days
(D) 16 4/11 days
(E) none of these
(A)