Aptitude - Pipes and Cistern - Discussion
Discussion Forum : Pipes and Cistern - General Questions (Q.No. 4)
4.
Two pipes A and B can fill a cistern in 37
minutes and 45 minutes respectively. Both pipes are opened. The cistern will be filled in just half an hour, if the B is turned off after:
minutes and 45 minutes respectively. Both pipes are opened. The cistern will be filled in just half an hour, if the B is turned off after:
Answer: Option
Explanation:
Let B be turned off after x minutes. Then,
Part filled by (A + B) in x min. + Part filled by A in (30 -x) min. = 1.
 x |
 |
2 | + | 1 |  |
+ (30 - x). | 2 | = 1 |
| 75 | 45 | 75 |
 |
11x | + | (60 -2x) | = 1 |
| 225 | 75 |
11x + 180 - 6x = 225.
x = 9.
Discussion:
90 comments Page 5 of 9.
Ratih said:
1 decade ago
I still don't get the logic. Why you talk about minutes needed and suddenly talk about part.
You can't write it "=1".
You can't write it "=1".
Saurav said:
1 decade ago
Why x*(A+B)+A*(30-x) = 1.
It should be x*(A+B)+A*(30-x) = 1/2, because after 30 mins the tank should be half filled?
It should be x*(A+B)+A*(30-x) = 1/2, because after 30 mins the tank should be half filled?
Sandip said:
1 decade ago
Here " 1 " means the complete part of the cistern....we learnt such theory in early school days.
ASIF said:
1 decade ago
Simply.
(1-Given time/A's time)*B's time.
= (1-30/75/2)45.
= (1-60/75)*45.
= (1-0.8)*45.
= 0.2*45 = 9.
(1-Given time/A's time)*B's time.
= (1-30/75/2)45.
= (1-60/75)*45.
= (1-0.8)*45.
= 0.2*45 = 9.
Charly said:
3 years ago
A = 75/2=>2/75,
B = 45=>1/45.
x(2/75+1/45) + (30-x)2/75 =1.
11x + 180-6x=225.
x = 9.
B = 45=>1/45.
x(2/75+1/45) + (30-x)2/75 =1.
11x + 180-6x=225.
x = 9.
(14)
Khagendra said:
8 years ago
@Kasi Srinivas.
Nice explanation, anyone can easily understand this, Thanks.
Nice explanation, anyone can easily understand this, Thanks.
Sarika said:
7 years ago
I didn't get this sum please give me some tricks to understand the problem.
Gunjan said:
5 years ago
Y(1-t/x).
X = 75/2.
Y =45.
T = 30.
This is the formula for this question.
X = 75/2.
Y =45.
T = 30.
This is the formula for this question.
Swetha said:
1 decade ago
How Part filled by (A + B) in x min + Part filled by A in (30 -x) min = 1?
Sameera said:
1 decade ago
1 indicates complete work, a+b=1 means a and b have done a complete work.
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