A and B alone can do a piece of work in 7 days and 14 days respectively. In how many days the work will be completed if they both work on alternate days starting with A?
Show answer & explanation
Correct answer: A
Explanation
The correct answer is option 1 i.e. 9.
A alone can do a piece of work = 7 days
B alone can do a piece of work = 14 days
So, the total work = LCM of 7 and 14 = 14 unit
Efficiency of A and B = 14/7 = 2unit per day, 14/14 = 1 unit per day
Two days work of A and B = 2 + 1 = 3 unit
2 days = 3 unit
So, 8 days = 12 unit
Remaining work = 14 - 12 = 2 unit
So, it is done by A = 2/2 = 1 day
Total days = 8 + 1 = 9 days