The Malibu Country Club needs to drain its pool for

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AAPL: Moderator; Posts: 2632; Joined: Sun Oct 29, 2017 2:08 pmFollowed by: 2 members

by AAPL » Sat Sep 15, 2018 7:59 am

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Veritas Prep

The Malibu Country Club needs to drain its pool for refinishing. The hose they use to drain it can remove 60 cubic feet of water per minute. If the pool is 80 feet wide by 150 feet long by 10 feet deep and is currently at 80% capacity, how long will it take to drain the pool?

A. 24 hours
B. 26 2/3 hours
C. 30 hours
D. 33 1/3 hours
E. 160 hours

OA B.

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Source: Beat The GMAT — Problem Solving | Sat Sep 15, 2018 7:59 am

fskilnik@GMATH: GMAT Instructor; Posts: 1449; Joined: Sat Oct 09, 2010 2:16 pmFollowed by: 33 members; Thanked: 59 times

by fskilnik@GMATH » Sat Sep 15, 2018 4:50 pm

AAPL wrote:Veritas Prep

The Malibu Country Club needs to drain its pool for refinishing. The hose they use to drain it can remove 60 cubic feet of water per minute. If the pool is 80 feet wide by 150 feet long by 10 feet deep and is currently at 80% capacity, how long will it take to drain the pool?

A. 24 hours
B. 26 2/3 hours
C. 30 hours
D. 33 1/3 hours
E. 160 hours

Excellent opportunity to use UNITS CONTROL, one of the most powerful tools of our method!

\[\frac{{60\,\,{\text{f}}{{\text{t}}^3}}}{{1\,\,\min }}\]
\[\frac{4}{5}\left( {80 \cdot 150 \cdot 10} \right)\,\,\,{\text{f}}{{\text{t}}^3}\,\,\,\,\, \leftrightarrow \,\,\,\,?\,\,{\text{h}}\]
\[?\,\,\, = \,\,\,\frac{4}{5}\left( {80 \cdot 150 \cdot 10} \right)\,\,\,{\text{f}}{{\text{t}}^3}\,\,\,\left( {\frac{{1\,\,\min }}{{60\,\,{\text{f}}{{\text{t}}^3}}}\,\,\begin{array}{*{20}{c}}
\nearrow \\
\nearrow
\end{array}} \right)\,\,\,\left( {\frac{{1\,\,{\text{h}}}}{{60\,\,\min }}\,\,\begin{array}{*{20}{c}}
\nearrow \\
\nearrow
\end{array}} \right)\]
Obs.: arrows indicate licit converters.
\[? = \,\,\underleftrightarrow {\frac{{4 \cdot 80 \cdot 150 \cdot 10}}{{5 \cdot 60 \cdot 60}}}\,\, = \,\,\frac{{4 \cdot 8 \cdot 30}}{{6 \cdot 6}} = \frac{{80}}{3} = \frac{{60 + 18 + 2}}{3} = 26\frac{2}{3}\,\,{\text{h}}\]

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

Regards,
Fabio.

Fabio Skilnik :: GMATH method creator ( Math for the GMAT)
English-speakers :: https://www.gmath.net
Portuguese-speakers :: https://www.gmath.com.br

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Scott@TargetTestPrep: GMAT Instructor; Posts: 8136; Joined: Sat Apr 25, 2015 10:56 amFollowed by: 29 members; Location: Los Angeles, CA; Thanked: 43 times

by Scott@TargetTestPrep » Wed Sep 19, 2018 5:10 pm

AAPL wrote:Veritas Prep

The Malibu Country Club needs to drain its pool for refinishing. The hose they use to drain it can remove 60 cubic feet of water per minute. If the pool is 80 feet wide by 150 feet long by 10 feet deep and is currently at 80% capacity, how long will it take to drain the pool?

A. 24 hours
B. 26 2/3 hours
C. 30 hours
D. 33 1/3 hours
E. 160 hours

The amount of water that needs to be drained is:

80 x 150 x 10 x 4/5 = 80 x 150 x 8 = 96,000 ft^3

It will take 96,000/60 = 9600/6 = 1600 minutes, or 1600/60 = 80/3 = 26 2/3 hours, to drain the pool.

Answer: B

Scott Woodbury-Stewart
Founder and CEO
[email protected]

See why Target Test Prep is rated 5 out of 5 stars on BEAT the GMAT. Read our reviews

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[email protected]: Elite Legendary Member; Posts: 10392; Joined: Sun Jun 23, 2013 6:38 pmFollowed by: 511 members; Location: Palo Alto, CA; Thanked: 2867 times; GMAT Score:800

by [email protected] » Wed Sep 19, 2018 8:30 pm

Hi All,

We're told that a The Malibu Country Club needs to drain its pool for refinishing. The hose they use to drain it can remove 60 cubic feet of water per MINUTE, the pool is 80 feet wide by 150 feet long by 10 feet deep and is currently at 80% full. We're asked how long it will, in HOURS, to drain the pool. This question is essentially a big 'rate' question, but the answer choices are sufficiently 'spread out' that you can take advantage of them and avoid doing a gigantic calculation.

To start, the current amount of water in the pool is (80)(150)(10)(.8) cubic feet. While that is a lengthy calculation, here's how you can make it easier...

Since we're multiplying 4 numbers together, it does NOT matter what order we do the multiplying... Thus, we can start with (80)(.8) = 64.

(64)(150)(10) = cubic feet of water

The rate of the hose is 60 cubic feet per MINUTE. Notice how 64 is just a bit bigger than 60. Thus, it will take a little more than (150)(10) = 1500 minutes to empty the pool. 1500/60 = 150/6 = 25 hours. Thus, we need answer that is a bit bigger than 25 hours. There's only one answer that matches.

Final Answer: B

GMAT assassins aren't born, they're made,
Rich

Contact Rich at [email protected]

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