Question : A and B together can do a piece of work in 12 days, while A alone can do the same work in 30 days. B alone can do it in:
Option 1: 18 days
Option 2: 20 days
Option 3: 15 days
Option 4: 22 days
Correct Answer: 20 days
Solution :
Given:
Time taken by A and B together to complete the work = 12 days
⇒ Part of work done by A and B in a day =
Time taken by A alone to complete the work = 30 days
⇒ Part of work done by A alone in a day =
Let the time taken by B alone to do the job =
⇒ Part of the job done by B alone in 1 day =
So,
⇒
So, the time taken by B alone to complete the work =
Hence, the correct answer is 20 days.
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