Aptitude - Pipes and Cistern - Discussion
Discussion Forum : Pipes and Cistern - General Questions (Q.No. 7)
7.
A tank is filled in 5 hours by three pipes A, B and C. The pipe C is twice as fast as B and B is twice as fast as A. How much time will pipe A alone take to fill the tank?
Answer: Option
Explanation:
Suppose pipe A alone takes x hours to fill the tank.
| Then, pipes B and C will take | x | and | x | hours respectively to fill the tank. |
| 2 | 4 |
 |
1 | + | 2 | + | 4 | = | 1 |
| x | x | x | 5 |
 |
7 | = | 1 |
| x | 5 |
x = 35 hrs.
Discussion:
33 comments Page 1 of 4.
Subhasis Mishra said:
4 years ago
A's 1 hr work = x,
B's 1 hr work = 2x,
C's 1 hr work = 4x,
Then, x+2x+4x = 1/5.
So,x = 1/35.
A can fill the tank in 35 hours.
B's 1 hr work = 2x,
C's 1 hr work = 4x,
Then, x+2x+4x = 1/5.
So,x = 1/35.
A can fill the tank in 35 hours.
(18)
Nikhil said:
5 years ago
The pipe C is twice as fast as B.
Means ratio of C:B = 2:1.
B is twice as fast as A.
Means B:A = 2:1.
Combine ratio of A:B:C = 1:2:4.
NOW,
The tank is filled in 5 hours by A,B,C.
so the addition of ratio =7(total parts of the tank)
So, 7*5 =35 hours to fill.
Now we have to find A's time.
A's ratio is 1. So divide 35by 1 =35 is the answer.
Means ratio of C:B = 2:1.
B is twice as fast as A.
Means B:A = 2:1.
Combine ratio of A:B:C = 1:2:4.
NOW,
The tank is filled in 5 hours by A,B,C.
so the addition of ratio =7(total parts of the tank)
So, 7*5 =35 hours to fill.
Now we have to find A's time.
A's ratio is 1. So divide 35by 1 =35 is the answer.
(8)
Rkay said:
2 years ago
R*T = w
(4+2+1) * 5 = w
7*5 = w
W = 35
An efficiency = 1
Time taken = 35/1 = 35.
(4+2+1) * 5 = w
7*5 = w
W = 35
An efficiency = 1
Time taken = 35/1 = 35.
(6)
Ritwik said:
6 years ago
B is twice as fast as A so if A=x, B=2x then how x/2?
(3)
Trishali said:
5 years ago
Basically they have used the concept of speed is inversely proportional to time. The question talks about how fast the pipes can fill the tank. Given that ratio, we inverse it to find the time.
So, A takes x hrs, B will take X/2 hrs because it is twice as fast as A and C will take x/4 hrs.
Now summation of work done by each pipe in 1 hr = (1/x+2/x+3/x) =7/x=1/5;.
So, from here x=35.
So, A takes x hrs, B will take X/2 hrs because it is twice as fast as A and C will take x/4 hrs.
Now summation of work done by each pipe in 1 hr = (1/x+2/x+3/x) =7/x=1/5;.
So, from here x=35.
(2)
Vineeth said:
7 years ago
Considering the value of A as X, B as 2X and C as 4X. Can anybody help me in solving this ?
(2)
Nitish said:
1 decade ago
As pipe C is twice as fast as B and B is twice as fast as A so if a fill the tank in x min.
As B is Two Time Faster not slower so it will take half time less than A that's why we have taken pipe B will fill in x/2 hours in less time compared to A.
As B is Two Time Faster not slower so it will take half time less than A that's why we have taken pipe B will fill in x/2 hours in less time compared to A.
(1)
YOGI M said:
9 years ago
[A + B + C] = 1/5.
According to question;
C = 2B = 4A----------- 2(2A )= 4A.
B = 2A.
[A] = ?
A + B + C = 1/5.
A + 2A + 4A = 1/5,
7A = 1/5,
A = 1/7 * 5,
A = 1/35 ==> 35hr.
According to question;
C = 2B = 4A----------- 2(2A )= 4A.
B = 2A.
[A] = ?
A + B + C = 1/5.
A + 2A + 4A = 1/5,
7A = 1/5,
A = 1/7 * 5,
A = 1/35 ==> 35hr.
(1)
Naveencool said:
9 years ago
Take A as x = 1, B = 2, C = 4.
The total is 7, each contribution is in 5 hours. Then 7 * 5 = 35 hours.
The total is 7, each contribution is in 5 hours. Then 7 * 5 = 35 hours.
(1)
SABYASACHI said:
1 decade ago
@Abhishek. We are calculating per hour, that's why we are taking the reverse of (x, x/2, x/4)...
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