An inlet pipe can fill an empty tank in 120 hours while an outlet pipe drains a completely-filled tank in 54 hours. If 8 inlet pipes and 3 outlet pipes are opened simultaneously, when the tank is empty, then in how many hours will the tank get completely filled?
Show answer & explanation
Correct answer: D
Explanation
The correct answer is option 4 i.e. 90
Given:
A inlet pipe can fill the empty tank in = 120 hours
An outlet pipe can emty the completly filled tank in = 54 hours
Concept Used:
Total work = Efficiency × Time
Explanation:
Let the total capacity of the tank be LCM (120, 54) = 1080
The efficiency of inlet pipe = 1080/120 = 9
The efficiency of an outlet pipe = 1080/54 = 20
According to the question
⇒ (8 inlet + 3 outlet) × time = 1080
⇒ (8 × 9 + 3 × -20) × time = 1080
⇒ (72 - 60) × time = 1080
⇒ time = 1080/12 = 90 hours