Two inlet pipes lead into a large water tank. First pipe can fill the tank in 1 hour 20 minutes; the

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21 Jan 2022 Pipes & Cisterns

Two inlet pipes lead into a large water tank. First pipe can fill the tank in 1 hour 20 minutes; the second pipe can fill it in 50 minutes. At 10:20 am, the first pipe is opened. At what time second one should be opened so that tank gets full by 11:00 am ?

OPtion

1) 10:45
2) 10:40
3) 10:30
4) 10:50
5) 10:25
6) 10:55
7) 10:35
8) 10:42
9) 10:54
10) None of these

Solution

Starting from 10:20 am, tank is to be filled by 11:00 am i.e. in 40 min.
Filling capacity per minute of first pipe=1/80 and of second pipe=1/50
First pipe will fill for total 40 min. and second say opened after 't' min, then 40*(1/80) + (40-t)*(1/50) = 1
Solving, we get t=15
Therefore, second pipe is opened after 15 minute i.e. at 10:35 am.

Correct Option: 7 Best Solution (2)

Varun   2 years AGO

First one is open for 40 minutes
which actually takes 80 minutes to fill full
=> half filled by first pipe
Rest half seconds one can fill in 50/2 = 25 minutes
So it is enough if it opened at 11AM-25 minutes = 10:35
Option (7)

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somya singh   2 years AGO

Pipe A would fill half of the tank in 40 minutes.
so, pipe B will need to fill only half of the tank . As so it has to be opened 25 minutes before 11 am . i.e., at 10:35 am

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