Question
Download Solution PDFTo complete a task, A takes 15 days whereas B takes 21 days. If they work alone on alternate days by turn, B starting on the first day, the number of days required to complete the task is
Answer (Detailed Solution Below)
Detailed Solution
Download Solution PDFGiven :- A takes 15 days whereas B takes 21 days to complete a task and they work alone on alternate days by turn, B starting on the first day.
Concept used :- A completes 1/15 task in one day.
B completes 1/21 task in one day.
Solution :- As B starts the first day
on 1st day 1/21 task is completed.
on 2nd day 1/21 + 1/15 task is completed.
on 3rd day 1/21 + 1/15 + 1/21 task is completed.
on 4th day 1/21 + 1/15 + 1/21 + 1/15 task is completed.
on 5th day 1/21 + 1/15 + 1/21 +1/15 + 1/21 task is completed.
on 6th day 3/21 + 3/15 ask is completed.
...
on 16th day 8/21 + 8/15 = 32/35 task is completed
on 17th day 32/35 + 1/21 = 101/105 task is completed.
So it would take \(17 \frac{4}{7}\) days
Last updated on Jun 23, 2025
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