Aptitude - Pipes and Cistern - Discussion
Discussion Forum : Pipes and Cistern - General Questions (Q.No. 10)
10.
Two pipes A and B can fill a tank in 15 minutes and 20 minutes respectively. Both the pipes are opened together but after 4 minutes, pipe A is turned off. What is the total time required to fill the tank?
Answer: Option
Explanation:
| Part filled in 4 minutes = 4 |  |
1 | + | 1 |  |
= | 7 | . |
| 15 | 20 | 15 |
| Remaining part = | |
1 - | 7 | |
= | 8 | . |
| 15 | 15 |
| Part filled by B in 1 minute = | 1 |
| 20 |
 |
1 | : | 8 | :: 1 : x |
| 20 | 15 |
| x = | |
8 | x 1 x 20 | |
= 10 | 2 | min = 10 min. 40 sec. |
| 15 | 3 |
The tank will be full in (4 min. + 10 min. + 40 sec.) = 14 min. 40 sec.
Discussion:
37 comments Page 3 of 4.
Sandy said:
9 years ago
Super solution @Kalpna.
Ashim said:
9 years ago
LCM of 15 & 20 is 60.
(4 + 3) * 4 = 28.
60 - 28 = 32.
4 + 32/3 =14min = 40sec.
(4 + 3) * 4 = 28.
60 - 28 = 32.
4 + 32/3 =14min = 40sec.
Venky said:
8 years ago
Can anyone explain it in easy method?
Varsha said:
8 years ago
Why equating with 1?
Manisha said:
8 years ago
It is clear now Thank you, @Ashim.
Leela said:
8 years ago
Can anyone tell me why do we equate to one?
D Priya said:
8 years ago
@Leela.
To fulfil the condition they equate to 1. A part of work + remaining part of work = 1. To be precise, you and your friend are doing a work by sharing. You completed half the work and your friend completed half the remaining work. Ie 1/2 + 1/2 = 1.
This logic is being used in this kind of problems.
To fulfil the condition they equate to 1. A part of work + remaining part of work = 1. To be precise, you and your friend are doing a work by sharing. You completed half the work and your friend completed half the remaining work. Ie 1/2 + 1/2 = 1.
This logic is being used in this kind of problems.
Kailash sharma said:
8 years ago
a=15;
b=20;
l.c.m of 15,20=60;
a's 1Min=60/15 => 4;
b's 1Min=60/20 => 3;
(a+b)'s 4Min= (4+3)*4=28;
Now 60-28 = 32;
b remaining time = 32/3 => 10.66.
Now add 10.66+4 =>14.66.
b=20;
l.c.m of 15,20=60;
a's 1Min=60/15 => 4;
b's 1Min=60/20 => 3;
(a+b)'s 4Min= (4+3)*4=28;
Now 60-28 = 32;
b remaining time = 32/3 => 10.66.
Now add 10.66+4 =>14.66.
(9)
Debalina Roy said:
7 years ago
"1/20 :8/15 :: 1:x " I can't understand this. Please explain me.
(2)
Vinay kumar gupta said:
6 years ago
In the question, it asks about the time required. It is not asking about total time so the answer will be 10 minute and 40 seconds.
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