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Two water tanks, X and Y, were drained simultaneously. If X contained

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Joined: 02 Sep 2009
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Kudos [?]: 128912 [0], given: 12183

Two water tanks, X and Y, were drained simultaneously. If X contained [#permalink]

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New post 02 Sep 2017, 03:21
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Question Stats:

55% (01:18) correct 45% (00:57) wrong based on 81 sessions

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Two water tanks, X and Y, were drained simultaneously. If X contained 30 more gallons of water than Y, and both tanks became empty at the same time, how long did it take the tanks to empty?

(1) For ever gallon drained from tank Y, 2 gallons were drained from tank X.

(2) Tank Y was drained at a constant rate of 20 gallons per hour.
[Reveal] Spoiler: OA

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Kudos [?]: 128912 [0], given: 12183

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Joined: 30 Dec 2013
Posts: 11

Kudos [?]: 6 [0], given: 562

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Re: Two water tanks, X and Y, were drained simultaneously. If X contained [#permalink]

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New post 02 Sep 2017, 07:08
let Y contain "a" gallon of water and emptying rate be y gallon/hour
therefore x contain a+30 gallon of water. let the emptying rate be x gallon/ hour
time of emptying is same for both the tank
therefore time taken to empty tank Y with capacity a liter and with rate y gallon/hour= time taken to empty tank x with capacity (a+30)liter and with rate y gallon/hour
a/y=(a+30)/x
1st statement gives comparison between the two rates
x=2y
put in the above equation, a=30
sufficient

2nd statement just give y=20
not sufficient
therefore answer is A

Kudos [?]: 6 [0], given: 562

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Joined: 23 Aug 2017
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Kudos [?]: 6 [0], given: 4

Two water tanks, X and Y, were drained simultaneously. If X contained [#permalink]

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New post 02 Sep 2017, 20:56
(1) We see that tank X is drained 2 times faster than tank Y, so in order to end draining at the same time, X must contain double the water than Y.
X - Y = 30; X = 2Y => X = 60, Y = 30.
But we still don't know the drain rate yet, so we still can not calculate the time.
(2) alone is not sufficient, but it gave us the required rate. So the answer is C.

Kudos [?]: 6 [0], given: 4

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Joined: 17 Dec 2016
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Kudos [?]: 6 [1], given: 6

Re: Two water tanks, X and Y, were drained simultaneously. If X contained [#permalink]

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New post 03 Sep 2017, 07:16
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Time = Work/Rate

Given : Time for X = Time for Y

= Wx/Rx = Wy/Ry
= Wy+30/Rx=Wy/Ry

From (1) we will get the value of Wy but not the rate. Not sufficient.

From (2) we will get the value of Ry but not Wy. Not sufficient.

Together (1) & (2), sufficient.

Answer :C

Kudos [?]: 6 [1], given: 6

Re: Two water tanks, X and Y, were drained simultaneously. If X contained   [#permalink] 03 Sep 2017, 07:16
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Two water tanks, X and Y, were drained simultaneously. If X contained

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