Question : A1 alone can do a work in 12 days and A2 alone can do the same work in 15 days. With help of A3, they finish the same work in 5 days. In how many days A3 alone can do the same work?
Option 1: 16
Option 2: 20
Option 3: 24
Option 4: 27
Correct Answer: 20
Solution :
Time taken by A1 to do the work = 12 days
Part of work done by A1 in a day =
Time taken by A2 to do the work = 15 days
Part of work done by A2 in a day =
Let
Part of work done by A3 in a day =
Time taken by A1, A2 and A3 to do the work = 5 days
Part of work done by A1, A2 and A3 in a day =
⇒
⇒
⇒
⇒
⇒
Hence, the correct answer is 20.
