Latest TCS Aptitude Question SOLUTION: a cistern consists of 3 pipes. By the help of 1st and 2nd pie the tank gets filled in 10 hours and 15 hours respectively but by the help of 3rd pipe tank becomes empty in 5 hours.

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a cistern consists of 3 pipes. By the help of 1st and 2nd pie the tank gets filled in 10 hours and 15 hours respectively but by the help of 3rd pipe tank becomes empty in 5 hours. At 8 a.m., 1st pipe was opened. At 9 a.m., 2nd pipe was also opened with 1st. At 10 a.m., 3rd pipe was also opened with 1st and 2nd. When the tank becomes filled or empty?

Asked In TCS SIDDHARTHA OJHA (9 years ago)

Unsolved Read Solution (14)

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Mainak Dutta  (9 years ago)

cistern filled by first pipe in 1 hr=1/10and second pipe=1/15. cistern emptied by 3rd pipe= 1/5. tank filled from 8a.m-9a.m by first pipe=1/10. tank filled by first and second pipe from 9a.m-10a.m=(1/10+1/15)=1/6. tank filled in this 2hr=1/6+1/10=4/15. tank emptied in 1hr when all three pipes are open=[1/5-(1/10+1/15)]=1/30. time required to empty the tank= 4/15*30= 8 hours. i.e 6p.m

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RITESH KUMAR  (9 years ago)

the total work will be 30litre(lcm of 10,15,5)
A fill 3 liter in a hour
B fill 2 litre in a hour
C empty 6 liter in a hour
a+b+c will empty 1 litre in a hour
now a will fill liter 3 till 9 am
a and b will fill total 8 liter till 10 am
but working together they empty 1 liter in a hour
so they will empty 8 liter in 8 hour i.e. 10am+8 hr=6pm
they will empty tank till 6 pm

Is this solution Helpfull? Yes (23) | No (1)  

D.HARINATH REDDY  (9 years ago)

Tank is empty at 6 p.m.
let take x is hours of 1st pipe opened
if tank is empty(x/10)+((x-1)/15)-((x-2)/5)=0
then x=10 hrs. so at 6 p.m. tank is emptied.

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SHIVAM  (9 years ago)

let total tank capacity=30 L
in 1h 1st pipe can fill=3L
2nd pipe=2L
&(1st+2nd)pipes =5L
3rd pipes = -6L

so in 1hour total =+5-6= -1L
@9a.m tank has=3L water
@10 = 3L+5L=8L
@11=8L-1L=7L
so every hour tank looses 1L of water.
so @6p.m it will be empty.!!

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Tuhin Chakraborty  (9 years ago)

let 300lt be the capacity of tank.
now, for 1st pipe : 300/10=30lt/hr fills
for 2nd pipe : 300/15=20lt/hr fills
for 3rd pipe : 300/5=60lt/hr empties

so from 8am-9am, 30lt is filled
from 9-10 am, 30+20lt is filled
total = 30+(30+20)lt=80lt
from 10-11am, (30+20)lt is filled again
total =130lt
but now 3rd pipe is started which empties 60lt
so now total is 130-60=70lt

we can see now total outgoing is 10 more than incoming water flow so from now each hr 10lt will be emptied.
So 70/10=7hrs more from 11am
resulting to 6pm.

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Sappa Naresh  (9 years ago)

1st pipe can fill the tank in 10 hrs, so it'll fill 10% of the tank in 1 hour.
1st and 2nd together can fill it in x hours which is found by

1/10 + 1/15 = 1/x
=> x=6 hrs.
So in 1 hour, they'll together fill 1/6th of the remaining of the tank.
=> 1/6 * 90% of the tank = 15% . So now 25% of the tank is filled.
Now 1st , 2nd and 3rd can together fill in y hours which is given by
1/10 + 1/15 - 1/5= 1/y
=> y= 7.5hrs
Now, 100% of tank is filled in 7.5hrs.
so 75% of tank will be filled in 5.6 hrs
So THE TANK WILL BE FILLED AT TIME 10A.M.+5.6HRS = 3:36 P.M approximately.

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ARCHIE GUPTA  (9 years ago)

answer is it is filled
in 9 hours i.e 6pm

Is this solution Helpfull? Yes (1) | No (9)  

Arpan Sharma  (9 years ago)

ans is tank is getting emptied.

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shivi  (9 years ago)

soltn:- let capacity of cistern is x.
1st pipe fill the cistern in 1 hour= x/10.
2nd pipe fill the cistern in 1 hour= x/15.
3rd pipe can empty the cistern in 1 hour=x/5.
so from 8 a.m to 10 a.m total cistern filled = x/10+x/15 => x/6
In next hour 3rd pipe is opened for empty the cistern so that total fill water
=> x/6+x/6(both pipe 1 n 2 are also opend)-x/5= 2x/15.
so with in 3 hours cistern is filled = 2x/15
remaining cistern to fill x-2x/15= 13x/15 .
3 hours +18 hours for 12x/15+ 1.5 hour for x/15= 2x/15+12x/15+x/15=> x
so cistern will be filled 6:30 am on next day.

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Arun Prakash  (9 years ago)

Speed 30 20 -60(empty)
Time 10 15 -5
Dist 300 300 300 (L.C.M of 10,15,5)

At 8 am: 30litres/hr filled
At 9 am: 30 litres+20 litres/hr filled
At 10 am: =10 litres emptied from the already filled level ( 30+(30+20)-10=70)
At 11 am: 3 Pipes empties 10 litres/hr & we know that speed * time = distance
how much time it need to empty the 70 litres is
10*T= 70 ----> T=70/10=7 hours
7 hours from 11 am means it is 6 pm.

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keerthi  (9 years ago)

8 HOURS IS CORRECT

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Sandeep Singh  (9 years ago)

in 1 hr 10% of tank is filled
in 2nd hour 16.67 + 10=26.67% of tank is filled
for remaining 73.33 part
the tank eventually gets emptied in 1 hr i.e. at 11.00 am

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M.Damaris priscilla  (9 years ago)

Tank is empty..
LCM=(5,10,15)=30.
so total unit is 30 .
1st tank filled 3unit in 1hr
2nd tank filled 2unit in 1hr
3rd tank empties 6unit in 1hr..
so when 1st and 2nd get opened it fills upto 5unit ..
when 3rd tank is open at 10.00 a.m, it empties the tank bcoz 6>5 so no water is there...
so ans is tank is emptied..

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Mithilesh Singh  (8 years ago)

Tank will not get
empty . It will be filled...read the question again. Both option r there.

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