Bunuel wrote:

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)

Our high-level "quant" preparation starts here: https://gmath.net