Correct Answer - Option 4 : 60 hours
Given:
A is 50% more efficient than B.
Time is taken by A to finish the work = time taken by B – 15
Concept used:
Work = time × efficiency
When work done by A and B is the same, t ∝ 1/e; where ‘t’ is time and ‘e’ is efficiency.
Calculation:
The ratio of efficiency of A to B = 3 ∶ 2
The ratio of time of A to B = 2 ∶ 3
Then, time is taken by A to finish the task = time taken by B – 15
⇒ 2x = 3x – 15
⇒ x = 15
Time taken by A to finish work = 2x = 30 hrs
Then, time is taken by A to do double the work = 2 × 30 = 60 hours.
∴ Time is taken by A to finish double the work is 60 hours.