A and B alone can do a piece of work in 4 and 9 days, respectively. In how many days will the work be completed, if they both work on alternate days, starting with B?
Show answer & explanation
Correct answer: B
Explanation
The correct answer is option 2 i.e. 5.
Given:
A and B alone can do a piece of work in 4 and 9 days, respectively.
Calculations:
Total work (LCM of 4, 9) = 36 units
Efficiency of A = 36/4 = 9
Efficiency of B = 36/9 = 4
If they both work on alternate days, starting with B
In 2 days, total work completed = (4 + 9) = 13
In 5 days, total work completed = 13 × 2 + 4 = 30
The remaining work (36 - 30 = 6) will be completed in 6/9, i.e. 2/3 days
Hence, the total work completed by them in 5 days.