Aptitude - Pipes and Cistern - Discussion
Discussion Forum : Pipes and Cistern - General Questions (Q.No. 6)
6.
Two pipes can fill a tank in 20 and 24 minutes respectively and a waste pipe can empty 3 gallons per minute. All the three pipes working together can fill the tank in 15 minutes. The capacity of the tank is:
Answer: Option
Explanation:
| Work done by the waste pipe in 1 minute = | 1 | - |  |
1 | + | 1 |  |
| 15 | 20 | 24 |
| = | |
1 | - | 11 | |
| 15 | 120 |
| = - | 1 | . [-ve sign means emptying] |
| 40 |
 Volume of |
1 | part = 3 gallons. |
| 40 |
Volume of whole = (3 x 40) gallons = 120 gallons.
Discussion:
48 comments Page 2 of 5.
Mouni said:
1 decade ago
How did -1/40? Please explain it.
Rupinder kaur said:
1 decade ago
How did 11/120?
Arshiya said:
1 decade ago
11/120 is the time taken by two pipes to fill the tank.
Bhakta B Monger said:
1 decade ago
A = 20 minutes.
B = 24 minutes.
C = 3 gallons per minute.
*The statement states that all three pipes working together can fill the tank in 15 minutes.
Therefore we can express it as : A+B+C = 15 minutes.
Say A+B+C=X.
Then C = X- (A+B).
Hence C = 15 minutes - (A+B).
Making the values in the ratio one we get.
C = 1/15- (1/20 + 1/24).
= 1/15 - 11/120.
= - 3/120.
= -1/40.
Thus the part filled by pipe C = 40 minutes.
For the volume of tank:
Given:
Pipe C = 3 gallons per minute.
Which means, in 1 minute = 3 gallons.
Then in 40 minutes = x.
x = 40*3 = 120 gallons.
B = 24 minutes.
C = 3 gallons per minute.
*The statement states that all three pipes working together can fill the tank in 15 minutes.
Therefore we can express it as : A+B+C = 15 minutes.
Say A+B+C=X.
Then C = X- (A+B).
Hence C = 15 minutes - (A+B).
Making the values in the ratio one we get.
C = 1/15- (1/20 + 1/24).
= 1/15 - 11/120.
= - 3/120.
= -1/40.
Thus the part filled by pipe C = 40 minutes.
For the volume of tank:
Given:
Pipe C = 3 gallons per minute.
Which means, in 1 minute = 3 gallons.
Then in 40 minutes = x.
x = 40*3 = 120 gallons.
Dwarikesh Sharma said:
1 decade ago
(1/20)+(1/24)-3G = (1/15).
-3G = (1/15)-(1/20+1/24).
-3G = -3/120.
G = 1/120.
Capacity of Tank G=120 gallon.
-3G = (1/15)-(1/20+1/24).
-3G = -3/120.
G = 1/120.
Capacity of Tank G=120 gallon.
Sujit baji said:
10 years ago
(1/15 - 11/120) = -1/40 how? please explain it.
Ragi said:
10 years ago
15(x/20+x/24-3) = x.
(11x-120)/8 = x.
x = 40 gallon.
(11x-120)/8 = x.
x = 40 gallon.
Aniket said:
10 years ago
You can simply take the L.C.M of the values and get the result.
L.C.M of above values = 2x2x2x3x5 = 120.
L.C.M of above values = 2x2x2x3x5 = 120.
Sreeram said:
9 years ago
A and B.
Time: 20min and 24min.
Efficiency: 6 and 5.
Work done A+B in 1 min = 11.
Work done A+B in 15 min = 11*15 = 165.
Tank emptied by C in 15 min = 45.
= 165 - 45 = 120 gallons.
Time: 20min and 24min.
Efficiency: 6 and 5.
Work done A+B in 1 min = 11.
Work done A+B in 15 min = 11*15 = 165.
Tank emptied by C in 15 min = 45.
= 165 - 45 = 120 gallons.
Snhk said:
9 years ago
L.C.M of 20, 15, 24 = 120 unit total capacity.
1st pipe = 6 unit.
2nd pipe = 5 unit.
= 11 unit.
Total 120/15 = 8 unit.
3rd (-) pipe capacity = (11 - 8) = 3 unit.
As UTC 120.
3rd pipe can empty = 120/3 = 40 unit which is = 3 gallons per minute.
Hence the capacity of the tank (40*3) =120 gallons.
1st pipe = 6 unit.
2nd pipe = 5 unit.
= 11 unit.
Total 120/15 = 8 unit.
3rd (-) pipe capacity = (11 - 8) = 3 unit.
As UTC 120.
3rd pipe can empty = 120/3 = 40 unit which is = 3 gallons per minute.
Hence the capacity of the tank (40*3) =120 gallons.
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