A and B can do a work in 10 days and 15 days respectively. They worked together for 5 days, then B left the work and A alone did the remaining work. The whole work got completed in:
Answer & explanation
Correct answer: option 1
A and B can do a work in 10 days and 15 days respectively.
A's 1 day work = 1/10
B's 1 day work = 1/15
If they work together,
A and B one day work = 1/10 + 1/15 = (3+2)/30 = 5/30 = 1/6
For 5 days = 5* 1/6 = 5/6
Remaining work = 1/6
Time taken by A alone for 1/6 of work = (1/6) / (1/10) = 5/3
Total Time = 5 days + 5/3 days = 20/3 days
The correct answer is Option (1) → $6\frac{2}{3}$ days