A can finish a piece of work by working alone in 4 days. B, while working alone, can finish the same work in 12 days. If both of them work together, then in how many days will the work be completed?
Show answer & explanation
Correct answer: C
Explanation
The correct answer is option 3 i.e. 3.
Given that, time taken by A alone to finish the work = 4 days
time taken by B to finish the work = 12 days
Total work = Efficiency × Time taken
Let the total work to be done LCM(4, 12) be 12 units.
Efficiency of A = 12/4 = 3 units/day
Efficiency of B = 12/12 = 1 unit/day
Now, efficiency of A and B together, (A + B) = 3 + 1 = 4 units/day
Time taken by A and B together to finish the work = 12/(A + B)
⇒ 12/4 = 3 days