# Tips And Tricks And Shortcuts to Solve Pipes & Cisterns Questions

## Pipes and Cisterns Tips and Tricks & Shortcuts

Here, are quick and easy tips and tricks for you to solve Pipes and Cisterns questions quickly, easily, and efficiently in competitive exams.

• Tips and tricks to solve the Pipes and Cisterns questions

Pipes and Cisterns questions on are almost like Time and Work questions.
In pipes and cistern problems, the portion of the tank are filled or emptied is calculated and it is relatively same as the amount of work done in time and work problems. Similarly, time taken to fill or empty a tank completely or to a desired level is the time taken to do a piece of work. ## Type 1: Calculate time taken to fill a tank by two or more pipes

### Question 1.

Two pipes A and B are connected to a container. Pipe A can empty the container in 20 minutes and pipe B can empty the container in 30 minutes. Both A and B are opened together. Find out the time to empty the container completely?

Options:
A. 12 mins
B. 14 mins
C. 10 mins
D. 7 mins

#### Solution:

Let the size of the container be = 60 units [LCM (20, 30)]
Efficiency of pipe A = 60 / 20 = 3 units
Efficiency of pipe B = 60 / 30 = 2 units
Combined efficiency of pipe A and pipe B = 5 units/min
So, time required to empty the container with both pipes = 60 / 5 = 12 mins

## Type 2: Calculate time taken to fill a tank having a hole or leakage

### Question 1.

A pipe takes 5 hours to fill a water tank but because of leakage, it takes 3 hours more. Find out the number of hours taken by leakage pipe to empty the full water tank?
Options:
A. 40/3 hrs
B. 3/40 hrs
C. 3/47 hrs
D. 2/51 hrs

#### Solution:

Water tank filled in 5 hours = 1/5
Now, due to outlet pipe, 1 hour part filled = 1/8
Part of the water tank emptied in 1 hour = 1/5 – 1/8 = 3/40
So, the leak will empty the full water tank in 40/3 hrs

## Type 3: Calculate Time Taken When Pipes Are Opened For Different Periods

### Question 1:

There are three pipes A, B and C, which can fill the tank in 10 hours. All the three pipes were opened for together for 5 hours, C is closed and inlets A and B fill the remaining part in 12 hours. Find the time taken by C alone to fill the tank.

Options:

A. 18 hrs 7 mins
B. 17 hrs 8 mins
C. 18 hrs
D. 17 hrs

#### Solution:

Part of the tank filled by the pipes A, B and C in 1 hour = 1/10
Part of the tank filled by the pipes A, B and C in 5 hours = 5 * 1/10 = 5/10 = 1/2
Remaining portion of tank to be filled = 1 – ½ = ½
Now, when A and B are open
Part of the tank filled by A and B in 1 hour = 1 x ½ / 12 = 1/24
Therefore, part of the tank filled by C in 1 hour = 1/10 – 1/24 = 7/120
Time taken by C alone = 1/(7/120) = 120/7 hours which can be written as 17 hrs 8 mins