Aptitude preparation
Aptitude on Pipes and Cisterns
Aptitude questions and answers on Pipes and Cisterns


1. 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?


Correct Answer:Option
A
Explanation:
Job done by the hole in 1 hour = [ 1/2  3/7 ] = 1/14 .
So, hole can empty the pot in 14 hrs.
2. 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?


Correct Answer:Option
B
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.
3. 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?


Correct Answer:Option
D
Explanation:
Capacity of the drum = (12 × 13.5) litres = 162 litres.
Capacity of each pot = 9 litres.
Total pots needed = 162/9 = 18 .
4. 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?

A.

144 minutes

B.

139 minutes

C.

114 minutes

D.

152 minutes


Correct Answer:Option
A
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.
5. Two taps A and B can separately fill a tank in 60 minutes and 75 minutes respectively. Tap C will be used to empty the tank. If all the 3 taps are opened at a time, then the tank is full in 50 minutes. In how much time, PipeC alone can empty the tank?

A.

140 minutes

B.

130 minutes

C.

110 minutes

D.

100 minutes


Correct Answer:Option
D
Explanation:
Work done by pipeC in 1 min.
= [ 1/50  ( 1/60 + 1/75 ) ] = [ 1/50 3/100 ] =  1/100 .
So, pipeC alone can empty the tank in 100 minutes.
6. 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?

A.

14 minutes

B.

13 minutes

C.

11 minutes

D.

24 minutes


Correct Answer:Option
D
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.
7. 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?

A.

3 9/17 hours

B.

4 9/17 hours

C.

2 9/17 hours

D.

9/17 hours


Correct Answer:Option
A
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. 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?

A.

5.11 hours

B.

15.11 hours

C.

25.11 hours

D.

None


Correct Answer:Option
B
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.
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?

A.

5 hours

B.

15 hours

C.

25 hours

D.

35 hours


Correct Answer:Option
D
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.
10. 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?

A.

2 hrs 15 min

B.

5 hrs 15 min

C.

8 hrs 15 min

D.

None


Correct Answer:Option
C
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.
11. 3 taps A, B and C can fill a tank from empty to full in 40 hours, 30 hours and 20 hours respectively. When the tank is empty, all the three taps are opened. A , B and C waste solutions x,y and z respectively. What is the proportion of waste solution z in the liquid in the tank after 3 minutes?


Correct Answer:Option
C
Explanation:
Part filled by (A + B + C) in 3 minutes = 3 [ 1/40 + 1/30 + 1/20 ] = [ 3 × 13/120 ] = 13/40 .
Part filled by C in 3 minutes = 3/20 .
∴ Required ratio = [ 3/20 × 40/13 ] = 6/13 .
12. 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?


Correct Answer:Option
B
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.
13. A large tanker can be filled by two pipes A and B in 60 and 40 minutes respectively. How much time needed to fill the tanker from empty state if pipe B is used for half the time and pipe A and pipe B fill it together for the remaining half?


Correct Answer:Option
A
Explanation:
Partion filled by pipes(A + B) in 1 min = [ 1/60 + 1/40 ] = 1/24 .
If the tank is filled in n minutes.
Then, n/2 [ 1/24 + 1/40 ] = 1 ↔ [ n/2 × 1/15 ] = 1 ↔ n = 30 min.
14. The booster pump emptying capacity of the tank is 10 litres per minute higher than its filling capacity and the booster pump needs 8 minutes lesser to empty the tank than it needs to fill it. If the capacity of the tank is 2400 litres, find the filling capacity of the pump?


Correct Answer:Option
C
Explanation:
Let the filling capacity of the booster pump = n litres / min .
So, emptying capacity of the booster pump = (n + 10) litres/ min .
So, [ 2400/n  2400/(n+ 10) ] = 8 ↔ n² + 10n – 3000 = 0
↔ (n  50) (n + 60) = 0 ↔ n = 50.
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