Correct Answer - Option 4 : 9 days
Given:
A and B together completes the task in 10 days
B and C together completes the task in 15 days
A and C together completes the task in 18 days
Formula used:
Efficiency = Work/(Time Taken)
Calculation:
Total task = LCM of 10, 15 and 18 = 90 units
Efficiency of (A + B) = (90/10) = 9 units/day
Efficiency of (B + C) = (90/15) = 6 units/day
And Efficiency of (A + C) = (90/18) = 5 units/day
Now, (A + B) + (B + C) + (A + C) = 9 + 6 + 5
⇒ 2(A + B + C) = 20
⇒ (A + B + C) = 10 units/day
Time taken by (A + B + C) to complete the task = (90/10) = 9 days
∴ A, B and C together finish the task in 9 days.
