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# Aptitude - Pipes and Cistern - Discussion

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"Do not wait for leaders; do it alone, person to person."
- Mother Teresa
2.

Pipes A and B can fill a tank in 5 and 6 hours respectively. Pipe C can empty it in 12 hours. If all the three pipes are opened together, then the tank will be filled in:

[A].
 1 13 hours 17
[B].
 2 8 hours 11
[C].
 3 9 hours 17
[D].
 4 1 hours 2

Explanation:

 Net part filled in 1 hour 1 + 1 - 1 = 17 . 5 6 12 60

 The tank will be full in 60 hours i.e., 3 9 hours. 17 17

 Ang said: (Sun, Sep 26, 2010 12:31:49 AM) Why we didnt take ( 1/12 - (1/5+1/6) ). Here 12 is greater right?

 Karan Ratnaparkhi said: (Fri, Jan 7, 2011 01:15:45 PM) 1/12 is smaller dan other two

 Komal said: (Thu, Feb 10, 2011 01:18:06 AM) Why we take 17/60 as 60/17 in the next step ?

 Jyothi said: (Thu, Feb 24, 2011 09:28:37 AM) @komal net part in 1 hour is 17/60 part so in 60/17 hour the part will be 1 here 1 means tank is full..... its just like the time and wok concept...

 Obama Sells Credits For Banks said: (Fri, Apr 15, 2011 07:28:15 PM) Why we take 17/60 as 60/17 in the next step ?

 Sathya said: (Thu, Jun 2, 2011 02:45:18 AM) Can't understood. Explain clearly.

 Manasa said: (Sat, Jun 11, 2011 08:37:31 AM) Here pipes A and B are used for filling the tanks, A and B takes 5 and 6 hours respectively to fill the tank . for 1 hour ,A can fill 1/5th of the tank and B can fill 1/6th of the tank. now tank C is used foe emptying the tank(water is running off from the tank)..it can empty the tank in 12 hours..means for 1 hour it empties 1/12th of water from the tank NOTE: A and B are filling the tank whereas C is used for emptying the tank. therefore add A and B and subtract it from c now consider how much water gets filled in the tank in 1 hour, 1/5+1/6-1/12=17/60 for 1 hour----17/60 ? hours----1 (note: for 1 hour-- 17 parts got filled up out of 60 parts for "?"hours-- 60 parts get filled up out of 60 (60/60=1) Here 1 indicates tank gets filled) just by cross multiplying it (1*1)=(?*17/60) ?=(17/60)/(1*1) 60/17 hours it can fill the tank.

 Preeti said: (Tue, Sep 13, 2011 04:31:54 PM) Thanks Manasa. I got it clearly.

 Happy said: (Sat, Sep 17, 2011 11:12:31 AM) I can't understand how it is solved. 1/5+1/6-1/12 =17/60. Please help.

 Kaveri said: (Wed, Oct 5, 2011 02:29:35 PM) I can't understand how it is solved. 1/5+1/6-1/12 =17/60. Please help.

 Neha said: (Fri, Jan 20, 2012 01:07:49 AM) (1/5 + 1/6 - 1/12) = (6+5/30 - 1/12) = (11/30 -1/12) = (132-30/360) = (102/360)dividing numerator &denominator by 2 = (51/180)dividing numerator &denominator by 2 = (17/60)

 Deepi said: (Sun, Feb 5, 2012 07:05:27 PM) Hi guys use this concepts to find the solution in easily Concept 1: A fill tank in x hrs and B fill in Y hrs and C in z hrs means together fill=? A&B=X*y/x+y let that A&B ans as p then A,B&C=p*z/p+z Concept 2: A fill tank in x hrs and B empty in Y hrs then both together work how much time is to empty=? =x*y/y-x

 Rav said: (Thu, Feb 16, 2012 12:58:14 AM) Will it work in every case ?

 Divya said: (Sun, Feb 26, 2012 05:37:58 PM) Thanks manasa.

 Mageswari said: (Sun, Jul 29, 2012 11:26:23 AM) Thanks manasa your explanation is clear cut.

 Rohit said: (Mon, Aug 27, 2012 07:31:06 PM) Thanks neha.

 Kiran said: (Fri, Oct 12, 2012 11:07:30 PM) @kaveri 1/5+1/6+-1/12= L.C.M of 5,6,12=60 So 1/5+1/6-1/12 12+10-5 --------------= 17 60 -------- 60

 Alka said: (Wed, Oct 17, 2012 12:12:57 PM) @Happy. First of all take L.C.M of 5, 6, &12. Then divide this L.C.M with every numerator & multiply that value with denominator of same.