Answer: Option C
Whole work will be done by A and B in (3 x 5) = 15 days.
Answer: Option B
Ratio of times taken by A and B = 1 : 3.
The time difference is (3 - 1) 2 days while B take 3 days and A takes 1 day.
If difference of time is 2 days, B takes 3 days.
So, A takes 30 days to do the work.
Whole work will be done in (3 x 5) = 15 days.
Answer: Option D
Let A's 1 day's work = x and B's 1 day's work = y.
Hence, B alone shall finish the whole work in 60 days.