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One water pump can fill half of a certain empty tank in 3 hours. Anoth
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04 Jan 2012, 09:17
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One water pump can fill half of a certain empty tank in 3 hours. Another pump can fill half of the same tank in \(3\frac{1}{2}\) hours. Working together, how long will it take these two pumps to fill the entire tank? (A) \(1\frac{7}{13}\) (B) \(1\frac{5}{8}\) (C) \(3\frac{1}{4}\) (D) \(3\frac{3}{13}\) (E) \(3\frac{1}{2}\)
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Re: One water pump can fill half of a certain empty tank in 3 hours. Anoth
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04 Jan 2012, 09:59
36mba wrote: One water pump can fill half of a certain empty tank in 3 hours. Another pump can fill half of the same tank in \(3\frac{1}{2}\) hours. Working together, how long will it take these two pumps to fill the entire tank?
(A) \(1\frac{7}{13}\) (B) \(1\frac{5}{8}\) (C) \(3\frac{1}{4}\) (D) \(3\frac{3}{13}\) (E) \(3\frac{1}{2}\) One pump can fill a tank in 3 hours and another in 3.5 hours so the rate at which both can half fill the tank is (1/3+1/3.5) => 13/21 Thus half of the tank can be filled in 21/13 so for filling the complete tank => 21/13*2 = 42/13 (D)



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Re: One water pump can fill half of a certain empty tank in 3 hours. Anoth
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04 Jan 2012, 10:02
1st pump takes (3+3)=6 hours to fill the full tank 2nd pump takes (3.5+3.5)=7 hours to fill the full tank Therefore, 1/6 + 1/7= 1/T [T= time it will take if they work together to fill the tank] solving for T= 3 3/13=D



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Re: One water pump can fill half of a certain empty tank in 3 hours. Anoth
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04 Jan 2012, 10:45
1st pump, 1/2 tank > 3 hours, full > 6 hours. This implies rate of 1/6 tank/hr 2nd pump, 1/2 tank > 3.5 hours, full > 7 hours. This implies rate of 1/7 tank/hr Combined rate 1/6 + 1/7 = 13/42 For full tank > 1/(13/42) = 42/13 = 3 3/13 > D
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Re: One water pump can fill half of a certain empty tank in 3 hours. Anoth
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16 Feb 2015, 11:20
36mba wrote: One water pump can fill half of a certain empty tank in 3 hours. Another pump can fill half of the same tank in \(3\frac{1}{2}\) hours. Working together, how long will it take these two pumps to fill the entire tank?
(A) \(1\frac{7}{13}\)
(B) \(1\frac{5}{8}\)
(C) \(3\frac{1}{4}\)
(D) \(3\frac{3}{13}\)
(E) \(3\frac{1}{2}\) 1/A = .5/3 1/B = .5/ 3.5 1/A+1/B = .5/3+.5/3.5 = 1/6+1/7 = 13/42 so rate is 13/42 Work =1 Time = 1/ (13/42) = 42/13



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Re: One water pump can fill half of a certain empty tank in 3 hours. Anoth
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16 Feb 2015, 18:01
Hi All, This question is an example of a "Work Formula" question; since it involves just two entities (in this case, water pumps), we can us the Work Formula to quickly get to the correct answer. We're told that 2 different water pumps can fill HALF of a tank in 3 hours and 3.5 hours, respectively. That means that the two pumps could fill the ENTIRE tank in 6 hours and 7 hours, respectively. Work = (A)(B)/(A+B) A = 6 hours B = 7 hours (6)(7)/(6+7) = 42/13 = 3 3/13 hours to fill the entire tank when working together. Final Answer: GMAT assassins aren't born, they're made, Rich
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Re: One water pump can fill half of a certain empty tank in 3 hours. Anoth
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30 Jan 2017, 03:05
1) First we need to find the rates of each pump individually: \(r*t=w, r1*3=1/2, r1=1/2*1/3=1/6; r2*7/2=1/2, r2=1/2*2/7=1/7\). 2) Then we need to combine the two rates, since the pumps are working simultaneously: \(1/6+1/7=13/42\) 3) Now we can find the time it takes the two of them to fill the tank: \(13/42*T=1\); \(T=42/13=3 \frac{3}{13}\)



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Re: One water pump can fill half of a certain empty tank in 3 hours. Anoth
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02 Feb 2017, 11:07
36mba wrote: One water pump can fill half of a certain empty tank in 3 hours. Another pump can fill half of the same tank in \(3\frac{1}{2}\) hours. Working together, how long will it take these two pumps to fill the entire tank?
(A) \(1\frac{7}{13}\)
(B) \(1\frac{5}{8}\)
(C) \(3\frac{1}{4}\)
(D) \(3\frac{3}{13}\)
(E) \(3\frac{1}{2}\) We are given that a water pump can fill half of a certain tank in 3 hours; thus, the rate of the pump is (1/2)/3 = 1/6. We are given that another pump can fill 1/2 of the same tank in 3½, or 7/2, hours. Thus, the rate of the second pump is (1/2)/(7/2) = 2/14 = 1/7. If we let t = the time it takes the two pumps working together to fill the entire tank, and if we let 1 equal the work (i.e., filling the entire tank) needed to be completed, we can create the following equation and determine t: (1/6)t + (1/7)t = 1 Multiplying the entire equation by 42, we have: 7t + 6t = 42 13t = 42 t = 42/13 = 3 3/13 Answer: D
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Re: One water pump can fill half of a certain empty tank in 3 hours. Anoth
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27 Jul 2018, 10:19
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Re: One water pump can fill half of a certain empty tank in 3 hours. Anoth &nbs
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