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( 1 ) Two taps can separately fill a cistern 10 minutes and 15 minutes respectively and when the waste pipe is open, they can together fill it in 18 minutes. The waste pipe can empty the full cistern in?
 1) 7 min
 2) 13 min
 3) 23 min
 4) 9 min

Show Answer Report Discussion in forumAnswer : 4) 9 min
Solution : 1/10 + 1/15  1/x = 1/18
x = 9
discussion
Answer : 4) 9 min



( 2 ) An electric pump can fill a tank in 3 hours. Because of a leak in the tank, it took 3 ½ hours to fill the tank. The leak can drain out of all the water of the tank in:
 1) 21 hrs
 2) 25 hrs
 3) 12 hrs
 4) 24 hrs

Show Answer Report Discussion in forumAnswer : 1) 21 hrs
Solution : Time taken = 3 hours
Time taken = 3 ½ hours
Time taken by A and B = 3*(3 1/2)/(3 1/2 3)
=> (21/2)/((7/2) 3)
=> (21/2)/((7 6)/2) = 21 hours
discussion
Answer : 1) 21 hrs



( 3 ) A cistern has a leak which would empty the cistern in 20 minutes. A tap is turned on which admits 4 liters a minute into the cistern, and it is emptied in 24 minutes. How many liters does the cistern hold?
 1) 480 liters
 2) 600 liters
 3) 720 liters
 4) 800 liters

Show Answer Report Discussion in forumAnswer : 1) 480 liters
Solution : Time taken to fill the tank is 1/20
Time taken to empty the taken is 1/24
Work done by the inlet in 1 minute = (1/20) (1/24) = 1/120
Therefore Volume = 120 X4 liters = 480 liters
discussion
Answer : 1) 480 liters



( 4 ) Two pipes X and Y fill a tank in 15 hrs. and 20 hrs. respectively, while a third pipe 'Z' can empty the full tank in 25 hrs. All the three pipes are opened in the beginning. After 10 hrs. Z is closed. In how much time, will the tank be full ?
 1) 12 hrs.
 2) 13 hrs
 3) 16 hrs.
 4) 18 hrs

Show Answer Report Discussion in forumAnswer : 1) 12 hrs.
Solution : Part filled in 10 hrs. = 10[(1/15)+(1/20)(1/25)] = 23/30
Remaining part = (1 (23/30)) = 7/30
(x + y )'s 1 hour work = [(1/15) + (1/20)] = 7/60
7/60 : 7/30 :: 1 : p
=> p=(7/30) * 1 * (60/7) = 2 hrs.
The tank will be full in (10 + 2) hrs = 12 hrs
discussion
Answer : 1) 12 hrs.



( 5 ) A cistern can be filled by pipe A and B in 12 minutes and 10 minutes respectively. The full tank can be emptied by a third pipe C in 8 minutes only. If all the taps be turned on at the same time, the cistern will be full in how much time?
 1) 15 1/7 Minutes
 2) 17 1/7 Minutes
 3) 19 1/7 Minutes
 4) 12 1/7 Minutes

Show Answer Report Discussion in forumAnswer : 2) 17 1/7 Minutes
Solution : Pipes A and B can fill a tank in 12 min and 10 min respectively
=>Part filled by pipe A in minute = 1?12
and Part filled by pipe B in minute = 1?10
Pipe C can empty it in 12 minute
=> Part emptied by pipe C in 1 minute = 1?8
Net part filled by Pipes A,B and C together in 1 minute = (1/12) + (1/10)  (1/8) = 7/120
i.e, the pipe can be filled in 120/7 = 17 1/7minute
discussion
Answer : 2) 17 1/7 Minutes



( 6 ) A leak in the lower portion of a tank can empty the full tank in 9 hrs. An inlet pipe fills water at the rtae of 10 lit. a minute. When the tank is full, the inlet is opened and due to leak, the tank is empty in 16 hrs. How many litres does the cistern hold ?
 1) 17,580
 2) 17,960
 3) 12,342
 4) 18,290

Show Answer Report Discussion in forumAnswer : 3) 12,342
Solution : Work done by the inlet in 1 hr = (1/9)  (1/16) = 7/144
Work done by the inlet in 1 min. = ((7/144) * (1/60)) = 78,640
Volume of 7/8,640 part = 10 litres.
Whole volume = 10 * 8,640/7 = 12,342 litres
discussion
Answer : 3) 12,342



( 7 ) Two pipes A and B can fill a tank in 9 hours and 3 hours respectively. If they are opened on alternate hours and if pipe A is opened first, how many hours, the tank shall be full?
 1) 4 hr
 2) 5 hr
 3) 2 hr
 4) 6 hr

Show Answer Report Discussion in forumAnswer : 2) 5 hr
Solution : Part filled by pipe P in 1 hour = 1/9
Part filled by pipe Q in 1 hour = 1/3
Pipe P and Q are opened alternatively.
Part filled in every 2 hour = (1/9) + (1/3) = (1 + 3)/9 = 4/9
Part filled in 4 hour = 2 * (4/9) = 8/9
remaining part =1  (8/9) = 1/9
Now it is pipe P's turn.
Time taken by pipe P to fill the remaining 1/9 part = (1/9)/(1/9) = 1 hour
Total time taken = 4 hour + 1 hour = 5 hour
discussion
Answer : 2) 5 hr



( 8 ) Two pipes A and B can fill a tank in 50 minutes and 60 minutes respectively. If both thepipes open together for 10 minutes, then A is closed. In how much time A fill the remaining tank?
 1) 38 Minutes
 2) 40 Minutes
 3) 33 Minutes
 4) 36 Minutes

Show Answer Report Discussion in forumAnswer : 1) 38 Minutes
Solution : Part filled by pipe A in 1 minute = 1/50
Part filled by pipe B in 1 minute = 1/60
Part filled by pipe A and pipe B in 1 minute = (1/50) + (1/60) = 11/300
Pipe A and pipe B were open for 10 minutes
Part filled by pipe A and pipe B in 10 minutes = 10 * 11/300 = 11/30
Remaining part = 1  (11/30) = 19/30
Time taken by pipe B to fill this remaining part = (19/30)/(1/60) = 38 minutes
discussion
Answer : 1) 38 Minutes



( 9 ) Pipe A can fill a tank in 8 hours, pipe B in 6 hours and pipe C in 24 hours. If all the pipes are open, in how many hours will the tank be filled?
 1) 2.4 hrs
 2) 3 hrs
 3) 4 hrs
 4) 4.2 hrs

Show Answer Report Discussion in forumAnswer : 1) 2.4 hrs
Solution : Part filled by pipe A in 1 minute = 1/8
Part filled by pipe B in 1 minute = 1/6
Part filled by pipe C in 1 minute = 1/12
Net part filled by (A+B+C ) in 1 minute = (1/8) + (1/6) + (1/12) = (3 + 4 + 2)/24 = 9/24 = 3/8
A, B and C pipes can fill the tank in 2.4 hr
discussion
Answer : 1) 2.4 hrs



( 10 ) Two pipes A and B can fill a tank is 8 minutes and 14 minutes respectively. If both the taps are opened simultaneously, and the tap A is closed after 3 minutes, then how much more time will it take to fill the tank by tap B?
 1) 6 min 15sec
 2) 5 min 45 sec
 3) 5 min 15 sec
 4) 6 min 30 sec

Show Answer Report Discussion in forumAnswer : 2) 5 min 45 sec
Solution : Part filled by pipe A in 1 minute = 1/8
Part filled by pipe B in 1 minute = 1/14
Part filled by pipe A and pipe B in 1 minute = (1/8) + (1/14) = 11/56
Pipe A and pipe B were open for 3 minutes
Part filled by pipe A and pipe B in 3 minutes = 3 * 11/56 = 33/56
Remaining part = 1  (33/56) = 23/56
Time taken by pipe B to fill this remaining part = (23/56)/(1/14) = 23/4 minutes = 5 3/4 minutes = 5 min 45 sec
discussion
Answer : 2) 5 min 45 sec
