A does 80% of a work in 20 days. He then calls in B and they together finish the remaining work in 3 days. How long B alone would take to do the whole work?
A) 75 days B) 37.5 days C) 17.5 days D) 35 days
Answers
Answer:
Suppose, there are 100 units of work to be completed.
‘A’ completes 80% of the work, that is, 80 units of work in 20 days.
A’s efficiency = 80/20 = 4 units of work per day
Total time taken by ‘A’ to complete 100 units of work = 100 / 4 = 25 days
If ‘A’ was to work alone, it would take him 25 days to complete 100 units of work (4 units per day).
But ‘B’ pitches in and they complete the remaining 20 units of work in 3 days.
‘A’ would have worked on his normal efficiency, finishing 12 units of work (4 units per day) in 3 days.
So, remaining 8 units of work would have been completed by ‘B’ in 3 days.
B’s efficiency = 8/3 units of work per day
Total time taken by ‘B’ to complete 100 units of work = 100 x 3/8 = 37.5 days
‘B’ would complete the task on 38th day.
so the answer is B) 37.5 days...