Question

Pipe A and pipe B can fill a tank in 3 hours and 4 hours respectively, and pipe C can empty it in 2 hours. If all the pipes are opened together, then in how much time tank can be filled?
1. 5 hours
2. 8 hours
3. 10 hours
4. 12 hours

Answer 1

Correct Answer - Option 4 : 12 hours

Given:

Time taken by pipe A to fill the tank = 3 hours

Time taken by pipe B to fill the tank = 4 hours

Time taken by pipe C to empty the tank = 2 hours

Concept:

If a tap can fill a tank in x hours, then the tank filled by the tap in 1 hour = 1 / x of the total tank.

Calculation:

Part of tank filled in 1 minute when all three pipes are opened simultaneously

⇒ (1 / 3) + (1 / 4) – (1 / 2)

⇒ (4 + 3 – 6) / 12

⇒ 1 / 12

∴ The tank can be filled in 12 hours.