Correct Answer - Option 2 : 127/7 hours
Given:
Time taken by inlet pipe to fill the tank = 4 hours
Time taken by outlet pipe to empty 3/7 of a tank = 3 hours
Formula used:
Efficiency = Total work/Time taken
Calculation:
LCM of 4 and 7 = 28 = Total work
Efficiency of inlet pipe = 28/4 = 7 work
Efficiency of outlet pipe = 28/7 = 4 work
Work done in 2 hours = (7 – 4) = 3 work
Time taken to do 27 work = (2/3) × 27 hours
⇒ 18 hours
Time taken more to complete remaining 1 work = 1/7 hour
Total time taken = 18 + (1/7) hours
⇒ 127/7 hours
∴ The total time taken to fill the tank is 127/7 hours
