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- Question
- Two taps can separately fill a cistern in 10 minutes and 15 minutes respectively and when the waste pipe is open, they can together fill it in 18 minutes. The waste pipe can empty the full cistern in?
Options- A. 7 minutes
- B. 9 minutes
- C. 13 minutes
- D. 23 minutes
- Correct Answer
- 9 minutes
ExplanationWork done by waste pipe in 1 min. = (1/10) + (1/15) - (1/18)
= (1/6) - (1/18) = 1/9
? Waste pipe can empty the cistern in 9 min. - 1. A cistern has two taps which fill it in 12 min. and 15 min. respectively. There is also a waste pipe in the cistern. When all the pipes are opened the empty cistern is full in 20 min. how long will the waste pipe take to empty a full cistern?
Options- A. 8 min.
- B. 10 min.
- C. 12 min.
- D. 16 min. Discuss
- 2. A tank be filled by one tap in 20 min. and by another in 25 min. Both the taps are kept open for 5 min. and then the second is turned off. In how many minutes more is the tank completely filled?
Options- A. 171/2 min.
- B. 12 min.
- C. 11 min.
- D. 6 min. Discuss
- 3. A pipe can fill a cistern in 12 min and another pipe can fill it in 15 min, but a third pipe can empty it in 6 min. The first two pipes are kept open 5 min in the beginning and then the third pipe is also opened.Time taken to empty the cistern is?
Options- A. 38 min
- B. 22 min
- C. 42 min
- D. 45 min Discuss
- 4. Two pipes A and B can fill a tank in 24 and 32 min, respectively. If both the pipes are opened together, after how much time pipe B should be closed so that the tank is full in 9 min?
Options- A. 40 min
- B. 30 min
- C. 10 min
- D. 20 min Discuss
- 5. A tap having diameter 'd' empty a tank in 40 min. How long another tap having diameter '2d' take to empty the same tank?
Options- A. 5 min
- B. 20 min
- C. 10 min
- D. 80 min Discuss
- 6. A tank is filled by a pipe A in 32 minutes and pipe B in 36 minutes. When full, it in can be emptied by a pipe C in 20 minutes. If all the three pipes are opened simultaneously, half of the tank will be filled in?
Options- A. 16 minutes
- B. 24 minutes
- C. 48 minutes
- D. None of these Discuss
- 7. Three pipes A, B and C can fill a cistern in 6 hours. After working at it together for 2 hours, C is closed and A and B can fill it in 7 hours. The time taken by C alone to fill the cistern is?
Options- A. 10 hours
- B. 12 hours
- C. 14 hours
- D. 16 hours Discuss
- 8. If two function simultaneously, the reservoir will be filled in 12 hours. One pipe fills the reservoir 10 hours faster than the other. How many hours does the faster pipe take to fill the reservoir?
Options- A. 25 hours
- B. 28 hours
- C. 30 hours
- D. 35 hours Discuss
- 9. Two pipes A and B can fill a tank in 15 hours and 20 hours respectively while a third pipe C can empty the full tank in 25 hours. All the three pipes are opened in the beginning. After 10 hours, C is closed. The time taken to fill the tank is?
Options- A. 12 hours
- B. 131/2
- C. 16 hours
- D. 18 hours Discuss
- 10. A cistern which could be filled in 9 hours takes one hour more to be filled owing to a leak in its bottom. If the cistern is full, in what time will the leak empty it?
Options- A. 80 hours
- B. 85 hours
- C. 90 hours
- D. 95 hours Discuss
Pipes and Cistern problems
Search Results
Correct Answer: 10 min.
Explanation:
Work done by waste pipe in 1 min. = (1/12 + 1/15) - 1/20
= (3/20 - 1/20) = 1/10
? Waste pipe can empty the cistern in 10 min.
Correct Answer: 11 min.
Explanation:
Work done by both the taps in 5 min
= 5 (1/20 +1/25) = (5 x 9)/100 = 9/20
Remaining part = (1 - 9/20) = 11/20
Now, 1/20 part is filled in 1 min.
So, 11/20 part will be filled in 11 min.
Hence, the tank will be full in 11 more min.
Correct Answer: 45 min
Explanation:
Let the number of minutes taken to empty the cistern be T min.
According to the questions,
T/6 - (T + 5)/12 - (T + 5)/15 = 0
? T/6 - T/12 - 5/12 - T/12 - T/12 - T/15 = 0
? T/6 - T/12 - T/15 = 5/12 + 5/15
? (10T - 5T - 4T)/ 60 = (25 + 20)/60
? T/60 = 45/60
? T = 45 min.
Correct Answer: 20 min
Explanation:
Here, A = 24 min, B = 32, T = 9 min
? Required time = B(1 - T/A )
= 32 ( 1 - 9/24 )
= 32 x 15/24 = 20 min.
Correct Answer: 20 min
Explanation:
Area of tap ? Work done by pipe.
When diameter is doubled, area will be four times. so, it will work four times faster.
Hence, required time taken to empty the tank = 40 x 1/4 = 10 min.
Correct Answer: None of these
Explanation:
Net filling in 1 min. = (1/32 + 1/36 - 1/20) = 13/1440
? Time taken to fill the tank = (1440/13) min.
Time taken to fill half of the tank = (1440/13) x 2 min. = (720/13) min.
= 555/13 min.
Correct Answer: 14 hours
Explanation:
Part filled in 2 hours = 2 x 1/6 = 1/3
Remaining part = (1 - 1/3) = 2/3
(A + B)'s 7 hour's work = 2/3
? (A + B)'s 1 hour's work = (2/3 x 1/7) = 2/21
(A + B + C)'s 1 hour's work = 1/6
C's 1 hours work = (1/6 - 2/21) = 1/14
Hence, C alone can fill the cistern in 14 hours.
Correct Answer: 30 hours
Explanation:
Suppose that one pipe takes N hours to fill the reservoir. Then another pipe takes (N - 10) hours.
? 1/N + 1/(N - 10) = 1/12
? 12(N - 10 + N) = N(N - 10)
or N2 - 34N + 120 = 0
or (N - 30)(N - 4) = 0
? N = 30 or N = 4
So, the faster pipe takes 30 hours to fill the reservoir.
Correct Answer: 12 hours
Explanation:
Part filled in 10 hours = 10 x (1/15 + 1/20 - 1/25) = 23/30
Remaining part = (1 - 23/30) = 7/30
Now, (1/15 + 1/20) part is filled by A and B in 1 hr.
7/30 part be filled them in (60/7) x (7/30) = 2 hrs.
? Total time taken to fill the tank = (10 + 2) hrs. = 12 hrs.
Correct Answer: 90 hours
Explanation:
Let the leak empty the full cistern in N hours
Now, applying the given rule (9 x N) / (N - 9) = 9 + 1
or N = 90 hours.
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