For more details go through the website http://www.mydearstudent.com/aptitude

1. Pipes and CisternsPipes and Cisterns
Questions and AnswersQuestions and Answers

2. 1) 13.5 litres capacity 12 Pots of water can be
sufficient to fill a drum. How many 9 litres pots of
water will be required to fill the above drum?
ANS:- 18
Explanation:-
Capacity of the drum = (12 × 13.5) litres = 162 litres.
Capacity of each pot = 9 litres.
Total pots needed = 162/9 = 18 .

3. 2) A Barrel can be filled by pipeA in 8 hours while
pipeB can be empty the Barrel in 17 hours. If both the
pipes start work at the same time, then find the time
needed to fill the Barrel?
Ans:- 15.11 hours
Explanation:-
Net partion filled in 1 hour = [ 1/8 - 1/17] = 9/136 .
The Barrel can be filled in 136/9 hrs = 15.11 hours.

4. 3) A tap can fill a tank in 16 hours. After half the tank is
filled, 3 more same capacity taps are opened. How much
time needed to fill the tank?
Ans:- 8 hrs 15 min
Explanation:-
• Time taken by one tap to fill half the tank = 8 hrs.
• Part filled by the four taps in 1 hour = 4 ×1/8 = 1/2 .
Remaining part = [ 1 - 1/2 ] = 1/2 .
• ∴ 1/2 : 1/2 : : 1 : A or A = [ 1/2 ×1 × 1/2 ] = 1/4
hrs i.e., 15 mins.
• So, total time taken = 8 hrs 15 min.

5. 4) A tap fill a pot in two hours because of a hole to the
pot, it took 2 1/3 hours. Calculate the time needed for
hole to emptied the pot completely?
Ans:- 14
Explanation:-
• Job done by the hole in 1 hour = [ 1/2 - 3/7 ] =
1/14 .
• So, hole can empty the pot in 14 hrs.

6. 5) Mug P has 3times more capacity than Mug Q. It
takes 60 turns for Mug P to fill the empty Drum. How
many turns it will take for both the Mugs P and Q,
having each turn together to fill the empty drum?
Ans:- 45
Explanation:-
Let capacity of Mug P be n litres.
Then, capacity of Mug Q = n/3 litres.
Capacity of the drum = 60n litres.
Required number of turns = [ 60n / ( n + n/3 ) ] = [
60n × 3/4n ] = 45.

7. 6)Pipe A can fill a tank in 5 hours and Pipe B can fill a
tank in 6 hours. Pipe C can empty the tank in 12 hours.
If all the three pipes are opened in the same time,
then the tank will be filled in?
Ans:- 3 9/17 hours
Explanation:-
Net portion filled in 1 hour = [ 1/5 + 1/6 - 1/12 ] =
17/60 .
So, The tank will be filled in 60/17 hrs i.e., 3 9/17
hours.

8. 7) PipeA fill a tank 3times faster than PipeB. If two
pipes can fill the tank in 36 minutes, then find the
time needed for PipeB alone to fill the tank?
Ans:- 144 minutes
Explanation:-
• Let us assume pipeB alone fill the tank in B minutes.
• Then, faster pipe will fill it in B/3 minutes.
• According to the question,
• 1/B + 3/B = 1/36 ↔ 4/B = 1/36 ↔ B = 144
min.
• So, pipeB can fill the tank in 144 minutes.

9. 8) Pipe X can fill a tank in 50 hours, Pipe Y in 100
hours and pipe Z in 300 hours. If all the pipes are
open, In how much time all 3 pipes fill the tank?
Ans:- 30
Explanation:-
Part filled by (X + Y + Z) in 1 hour = [ 1/50 + 1/100 +
1/300 ] = 1/30 .
∴ All the three pipes together will fill the tank in 30
hours.

10. 9) PipeA, PipeB and PipeC can fill a Cistern in 5 hours. The
pipe C is twice as fast as pipe B and pipe B is twice as fast
as pipe A. How much time will pipe A alone will take to fill
the Cistern?
Ans:- 35 hours
Explanation:-
• Suppose pipe A alone takes A hours to fill the Cistern.
• Then, pipes B and C will take A/2 and B/4 hours
respectively to fill the tank.
• So, 1/A + 2/A + 4/A = 1/5 ↔ 7/A = 1/5
A = 35 hrs.

11. 10) Two pipes A and B can fill a barrel in 40 and 60
minutes respectively. Find the time to fill the Barrel if
both the pipes are used?
Ans:- 24 minutes
Explanation:-
• Portion filled by pipeA in 1 min. = 1/40 ;
• Portion filled by pipeB in 1 min = 1/60 .
• Portion filled by pipes(A + B) in 1 min. = 1/40 + 1/60
= 1/24 .
• pipes A and B can fill the tank in 24 minutes.