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(#M40037877) SSC Numerical Ability question Pipes and cistern Keep an EYE

A can fill in 20 mins and B can empty in 30 mins . If A and B be kept open alternately for one minute each, how soon will the cistern be filled?

Asked In SSC Dayanand (10 years ago)

Solved Saraswathy Read Solution (7)

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Read Solution (7) :

Saraswathy  (10 years ago)

A ll fill 1/20 part of the tank in 1 min
B ll empty 1/30 part of the tank in 1 min
Assuming if A is opened at the 1st min nd B at the next min
1/20 - 1/30 = 1/60 part filled in 2 mins

1/60 part ----> 2
1 part ----> x
x = 60*2 = 120 mins

Ans : 120 mins

Is this solution Helpfull? Yes (7) | No (3)  

Devendra Marghade  (10 years ago)

119 min.

First A fills for 1 min.= 1/20 & then B empty for 1 min.=1/30
2 min. filling= (1/20)-(1/30)= 1/60
Filling upto 118 min. =(118/2)*(1/60)=59/60
So at 119 min. A will again fill= (59/60)+(1/20)=62/60 (cistren is filled)

Is this solution Helpfull? Yes (6) | No   

Dharmendra  (10 years ago)

Ans is 119 min

on last min there is already tank is full

Is this solution Helpfull? Yes (2) | No (1)  

pankaj narayan  (10 years ago)

115 minutes is the answer.
1/20-1/30 = 1/60 part in 2minutes ..
so 1/120 part in 1 minute ..
now A fills 1/20 part in a minute.
last time a fills ..then remaining will be 19/20 parts..
time required to fill 19/20 parts will be (19/20) / 1/120 = 114 minutes
total time = 114 + 1 minute = 115 minutes.

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SANTOSH  (9 years ago)

115mins

assume capacity of tank= l.c.m of 20,30=60 units
tap A fills 3 units/min
Tap B empty 2 units/min
so in 2 min i.e.1st min(tap A)+2nd min(tap B)=(3-2) = 1 units/min (say as) 1 cycle
1 cycle fills 1 units
for 57 cycles i.e in 114 mins fills 57 units
in next 115th min A pipe fills 3 units.....So total units (57+3)=60 completed....

Ans is 115min

Is this solution Helpfull? Yes (1) | No (2)  

krishna kanth  (10 years ago)

24 min

assume capacity of tank= l.c.m of 20,30=60 units
tap A allows 3 units/min
Tap B allows 2 units/min
so in 2 min i.e.1st min(tap A)+2nd min(tap B)=5 units/min (say as) 1 cycle
1 cycle fills 5 units
x cycles fills 60 units
x=60/5
x=12cycles
x=12*2 min=24 min

Is this solution Helpfull? Yes | No (3)  

Della David  (10 years ago)

120+130=I12
ANS IS 12

Is this solution Helpfull? Yes | No (5)  

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