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]

17 Sep 2005, 02:02

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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.

Like they used to say in math class, please show your work! OA to come!
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17 Sep 2005, 04:28

I would pick C.

Let G be the volume in Y, which means we have G+30 in container X.

1) For ever gallon drained from tank Y, 2 gallons were drained from tank X.
Insufficient, need the rates.

2) Tank Y was drained at a constant rate of 20 gallons per hour.
Insuff, we need the rate for X.

1, 2 combined yields, the rate of Y is 20 gallon/hour
and the rate of X is 40gallon/hour

So,
The time it takes is the same for both to get empty.

G/20 =(G+30)/40 -> G=30

The time can now be calculated. 30/20=60/40=1.5 hour.

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17 Sep 2005, 09:26

lets see..

X=y+30
y

so lets right the Workdone=Rate*time

y+30=rx*t

y=ry*t; where t is the same

(1) tells that rx=2ry

so

y+30=2ry*t
y=ry*t

solve simeltaneously...
30=ry*t

t=30/ry...we dont know ry...insuff

(2)
just tells ry...nothing else...insuff, we need to know the reltavitiy of y and x...

Combine...sufficient...

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17 Sep 2005, 10:08

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.

from 1+2), we get Y drains at 20g/hr, X drains at 40g/hr
X drains 20g/hr faster

30 gallons more were drained from X, it takes 30/20 = 1.5 hours

so C

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17 Sep 2005, 10:44

Got C as well.

Y = amount of water in Y
Y + 30 = amount of water in X

T = time for both to drain

Ry = rate of Y

Rx = rate of X

From Statement one you get

Rx = 2Ry

Set up the rate equations for both (Rate = amount/time), combine and you get

RyT = 30

Insufficient

From Statement two you just get the Ry, also insufficient.

Combine and you get T.

C.

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17 Sep 2005, 16:22

Good job you guys!! OA is C. You guys are hella smart!
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[#permalink] 17 Sep 2005, 16:22

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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

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

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