Correct Answer - Option 2 : 10 days
Given:
A alone can complete work = 18 days
B alone can complete work = 45 days
A and B start working together but B left after some time and A finish the remaining work in 4 days
Concept:
Total work = Time × Efficiency
Calculation:
|
Work done by
|
Time taken
(in day)
|
Efficiency
|
|
A
|
18
|
90/18 = 5
|
|
B
|
45
|
90/45 = 2
|
|
Total work = L. C. M. = 90
|
Start work together but B left after some time and A finish the remaining work in 4 days
Last 4 days work done by A = 4 × 5 = 20 unit
Work for did together = 90 – 20 = 70 unit
Efficiency of A and B = 5 + 2 = 7 unit
Let, After x days from the start B did leave the work
Then, x = 70/7 = 10 days
∴ After 10 days from the start B did leave the work
