A pipe can fill a petrol tank in 20 hrs but due to some leakage it got emptied…
2023
A pipe can fill a petrol tank in 20 hrs but due to some leakage it got emptied in 15 hrs. Find the time in which the tank will be completely full.
- A.
70
- B.
69
- C.
60
- D.
20
Attempted by 27 students.
Show answer & explanation
Correct answer: C
Key idea: compare the filling rate and the leak (emptying) rate.
Filling pipe rate = 1/20 tank per hour.
Leak emptying rate = 1/15 tank per hour.
Combined rate = filling rate − leak rate = 1/20 − 1/15 = (3 − 4)/60 = −1/60 tank per hour.
Because the combined rate is negative, the system is net emptying. The tank will not become full; instead a full tank would be emptied in 60 hours.
If the intended question was the time for the tank to become completely empty given both the filling pipe and the leak, the answer is 60 hours.