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# Two water tanks x and y were drained simultaneously. If x

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Two water tanks x and y were drained simultaneously. If x [#permalink]

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09 Apr 2009, 09:51
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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 every gallon drained from tank y, 2 gallons drained from x
(2) Tank y was drained at a constant rate of 20 gallongs/hour.
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09 Apr 2009, 14:54
jeevanchand wrote:
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 every gallon drained from tank y, 2 gallons drained from x
(2) Tank y was drained at a constant rate of 20 gallongs/hour.

X: y+30; (y+30)/R=t
Y: y; y/r=t
t=?

Stmt1: R=2r

(y+30)/2r=t
y/r=t

From the above, you will have tr=2tr-30
or tr=30

Insuff - we need r.

Stmt2; r=20 (gallon per hour)
Insuff.

Stmt 1&2:
tr=30
r=20
t=3/2 or 1.5 hours Suff
Hence, C.
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Name: Ronak Amin
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10 Apr 2009, 02:26
Agree with C. But I think there is a small glitch with the following explanation.
botirvoy wrote:
jeevanchand wrote:
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 every gallon drained from tank y, 2 gallons drained from x
(2) Tank y was drained at a constant rate of 20 gallongs/hour.

X: y+30; (y+30)/R=t
Y: y; y/r=t
t=?

Stmt1: R=2r
(y+30)/2r=t
y/r=t

From the above, you will have tr=2tr-30
or tr=30

Insuff - we need r.

Stmt2; r=20 (gallon per hour)
Insuff.

Stmt 1&2:
tr=30
r=20
t=3/2 or 1.5 hours Suff
Hence, C.

Last edited by Economist on 11 Apr 2009, 11:52, edited 1 time in total.
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10 Apr 2009, 05:11
OA is C.

Economist, I agree with botirvoy that R should be equal to 2r.

R = Water1/t
r = Water2/t

Water1 = 2 X Water2

So, R = 2r. Am I missing something?
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11 Apr 2009, 11:51
Sorry for the confusion:(
botirvoy is correct( and also you )...I will change my post...i confused 'rate' with 'time'.

If A works twice as fast as B then rate of A is twice that of B. ( R= 2r) AND
If A works twice as fast as B then time taken by A is half of the time taken by B.

So,in this example if t1 is time taken by Y and t2 is time taken by X(faster) then t2 = t1/2.
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13 Apr 2009, 18:36
yeah we need rate and volume.
Re: Water tanks   [#permalink] 13 Apr 2009, 18:36
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