A and B working together can do a work in 10 days. If A can do the work in 15 days, then how many days will B take to do the same work?
Answer & explanation
Correct answer: option 2
A and B working together can do a work in 10 days
A and B one day work = 1/10
A can do the work in 15 days
A's alone one day work = 1/15
Assume B takes T days to complete the work alone
B's one day work = 1/T
Thus, 1/10 = 1/15 + 1/T
1/T = 1/10 - 1/15 = (3-2)/30
T = 30 days
The correct answer is Option (2) → 30