Aptitude - Pipes and Cistern - Discussion
Discussion Forum : Pipes and Cistern - General Questions (Q.No. 8)
8.
Two pipes A and B together can fill a cistern in 4 hours. Had they been opened separately, then B would have taken 6 hours more than A to fill the cistern. How much time will be taken by A to fill the cistern separately?
Answer: Option
Explanation:
Let the cistern be filled by pipe A alone in x hours.
Then, pipe B will fill it in (x + 6) hours.
 |
1 | + | 1 | = | 1 |
| x | (x + 6) | 4 |
 |
x + 6 + x | = | 1 |
| x(x + 6) | 4 |
x2 - 2x - 24 = 0
(x -6)(x + 4) = 0
x = 6. [neglecting the negative value of x]
Discussion:
18 comments Page 2 of 2.
Vishwa said:
9 years ago
@Neha.
Let A = X , B= X+6.
Total Work= LCM of X, X+6 = X(X+6) ----->(1)
Work done by A in 1hr= X(X+6)/X = X+6.
Work done by B in 1hr= X(X+6)/X+6 =X.
Now the total work done by A and B in 1 hr: X+X+6 = 2X+6.
The total work should be completed in : eq(1)/2X+6 = x(X+6)/2X+6 = 4.
Now solving the quadratic eq x^2-2X-24 = 0.
Then, x= 6 answer, neglect -ve value.
Let A = X , B= X+6.
Total Work= LCM of X, X+6 = X(X+6) ----->(1)
Work done by A in 1hr= X(X+6)/X = X+6.
Work done by B in 1hr= X(X+6)/X+6 =X.
Now the total work done by A and B in 1 hr: X+X+6 = 2X+6.
The total work should be completed in : eq(1)/2X+6 = x(X+6)/2X+6 = 4.
Now solving the quadratic eq x^2-2X-24 = 0.
Then, x= 6 answer, neglect -ve value.
(5)
Paandu said:
8 years ago
1/A + 1/B = 1/4
a:b = 6:12 = 1:2;
a/b = 1/2.
Here we have to find b
b = 2a;(keep in the place of b)
1/a + 1/2a = 1/4
2 + 1/2a = 1/4
a = 6.
a:b = 6:12 = 1:2;
a/b = 1/2.
Here we have to find b
b = 2a;(keep in the place of b)
1/a + 1/2a = 1/4
2 + 1/2a = 1/4
a = 6.
(1)
Ajay said:
8 years ago
How x2-2x-24= (x-6) (x+4)? Please explain.
Leela said:
8 years ago
@Rashmibs.
Why do you subtract 1/4 from 1/6 to know b's actual part? According to your logic---- ( (a+b) - (b's part) ) will only give you a's part no?
Why do you subtract 1/4 from 1/6 to know b's actual part? According to your logic---- ( (a+b) - (b's part) ) will only give you a's part no?
(1)
Priya said:
8 years ago
How (x+6) will come?
(x-6) only will come.
(x-6) only will come.
Sakib said:
7 years ago
Please explain.
Abhijeet said:
6 years ago
If we take factor 12x 2 = 24.
10 and 2 is a factor.
And the answer will be 2.
10 and 2 is a factor.
And the answer will be 2.
(3)
Vaishnavi keshari said:
1 month ago
Let the time of A=x.
So the time of B will be x+6.
since time A : B = x : x+6.
therefore efficiency = x+6 : x.
total work = 4*(2x+6).
Since the difference of time is 6, so,
total work *(1/x-1/6+x) = 6,
x= 6 (time of A to filled the pipe alone).
So the time of B will be x+6.
since time A : B = x : x+6.
therefore efficiency = x+6 : x.
total work = 4*(2x+6).
Since the difference of time is 6, so,
total work *(1/x-1/6+x) = 6,
x= 6 (time of A to filled the pipe alone).
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