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1. while working 7 hour a day , A alone can complete a piece of work in 6 days and B alone in 8 days . In what time would they complete it together , 8 hour a day?
- A. 5 days
- B. 5 days
- C. 5 days
- D. 5 days
Answer: Option B
Explanation:
A can complete the work in 7*6 hrs = 42 hrs.
A can complete in 1 hr = 1/42 part.
B can complete the work in 7*8 hr = 56 hrs.
A&B together do in 1 hr = 1/42 + 1/56 = 7/168 = 1/24 part. So they will do in 8 hrs = 8*1/24 = 1/3 part.
Hence they need 1÷1/3 = 3 days to complete the work.
A can complete in 1 hr = 1/42 part.
B can complete the work in 7*8 hr = 56 hrs.
A&B together do in 1 hr = 1/42 + 1/56 = 7/168 = 1/24 part. So they will do in 8 hrs = 8*1/24 = 1/3 part.
Hence they need 1÷1/3 = 3 days to complete the work.
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