A certain liquid passes through a drain at a rate of w/20 ga

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A certain liquid passes through a drain at a rate of w/20 gallons every x seconds. At that rate, how many minutes will it take y gallons to pass through the drain?

A. y/(1200xy)
B. 20xy/w
C. xy/(3w(
D. w/(3xy)
E. 3y/(wx)

OA C

Source: Princeton Review

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by Jay@ManhattanReview » Fri Sep 14, 2018 3:34 am
BTGmoderatorDC wrote:A certain liquid passes through a drain at a rate of w/20 gallons every x seconds. At that rate, how many minutes will it take y gallons to pass through the drain?

A. y/(1200xy)
B. 20xy/w
C. xy/(3w)
D. w/(3xy)
E. 3y/(wx)

OA C

Source: Princeton Review
Give that liquid passes the drain at a rate of w/20 gallons every x seconds, the rate per second = w/(20x) gallons/second

Thus, seconds needed to pass y gallons = y / [w/(20x)] = 20xy / w

Minutes needed to pass y gallons = 20xy / (60w) = xy/3w gallons per minute

The correct answer: C

Hope this helps!

-Jay
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by fskilnik@GMATH » Fri Sep 14, 2018 6:18 am
BTGmoderatorDC wrote:A certain liquid passes through a drain at a rate of w/20 gallons every x seconds. At that rate, how many minutes will it take y gallons to pass through the drain?

A. y/(1200xy)
B. 20xy/w
C. xy/(3w)
D. w/(3xy)
E. 3y/(wx)
Excellent opportunity to use UNITS CONTROL , one of the most powerful tools of our method!

\[\frac{{\,\,\frac{w}{{20}}\,\,}}{x}\,\,\,\frac{{{\text{gallons}}}}{{\text{s}}}\,\,\, = \,\,\,\frac{w}{{20\,\,x}}\,\,\,\frac{{{\text{gallons}}}}{{\text{s}}}\]
\[?\,\,\,\min \,\,\, \leftrightarrow \,\,\,y\,\,\,{\text{gallons}}\,\]

\[?\,\,\, = \,\,\,y\,\,{\text{gallons}}\,\,\,\left( {\frac{{\,20\,\,x\,\,{\text{s}}\,}}{{w\,\,{\text{gallons}}}}\,\,\begin{array}{*{20}{c}}
\nearrow \\
\nearrow
\end{array}} \right)\,\,\,\,\,\left( {\frac{{\,1\,\,\min \,}}{{60\,\,{\text{s}}}}\,\,\begin{array}{*{20}{c}}
\nearrow \\
\nearrow
\end{array}} \right)\,\,\,\, = \,\,\,\,\frac{{20\,\,xy}}{{60\,\,w}}\,\,\, = \,\,\,\frac{{xy}}{{\,3w\,}}\,\,\,\,\,\,\,\,\left[ {\min } \right]\]
Obs.: arrows indicate licit converters.


This solution follows the notations and rationale taught in the GMATH method.

Regards,
Fabio.
Fabio Skilnik :: GMATH method creator ( Math for the GMAT)
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by Scott@TargetTestPrep » Thu Sep 27, 2018 4:42 pm
BTGmoderatorDC wrote:A certain liquid passes through a drain at a rate of w/20 gallons every x seconds. At that rate, how many minutes will it take y gallons to pass through the drain?

A. y/(1200xy)
B. 20xy/w
C. xy/(3w(
D. w/(3xy)
E. 3y/(wx)
The rate is (w/20)/x = w/(20x).

So y gallons will pass through the drain in y/(w/(20x)) = 20xy/w seconds, which is (20xy/w)/60 = 20xy/(60w) = xy/(3w) minutes.

Answer: C

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by [email protected] » Thu Sep 27, 2018 6:00 pm
Hi All,

We're told that a certain liquid passes through a drain at a rate of W/20 gallons every X SECONDS. We're asked how many MINUTES it would take Y gallons to pass through the drain. This question can be solved in a number of different ways, including by TESTing VALUES.

IF....
W=20 and X=2, then 20/20 = 1 gallon passes through every 2 seconds
Y = 30 gallons --> which would take 2(30) = 60 seconds = 1 minute
so we're looking for an answer that equals 1 when W=20, X=3 and Y=30. There's only one answer that matches....

Final Answer: C

GMAT assassins aren't born, they're made,
Rich
Contact Rich at [email protected]
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