A and B can do a work in 13 days and 26 days, respectively. If they work for a day alternately, starting with A, then in how many days will the work be completed?
Show answer & explanation
Correct answer: B
Explanation
The correct answer is Option 2 i.e. 17.
Time in which A can complete a piece of work = 13 days
Time in which B can complete a piece of work = 26 days
Total work (L.C.M. of 13 and 26) = 26 units
⇒ Amount of work done by A in 1 day = 26/13 = 2 units
⇒ Amount of work done by B in 1 day = 26/26 = 1 units
If A and B work alternatively, work done by them in 2 days = 3 units
⇒ Work done by then in 16 days = 8 × 3 = 24 units
⇒ Amount of Work left = 2 units
Work done by A on the 17th day = 2 units
Thus, the time taken to complete the work = 17 days