BTGmoderatorLU wrote:A rectangular-shaped carpet remnant that measures x feet by y feet is priced at $50. What is the cost of the carpet, in dollars per square yard? (9 square feet = 1 square yard)
A. 50xy
B. 450xy
C. xy / 9
D. xy / 50
E. 450 / (xy)
Source: GMAT Prep
Excellent opportunity to use UNITS CONTROL, one of the most powerful tools of our course!
\[9\,\,{\text{f}}{{\text{t}}^2}\,\,\, \leftrightarrow \,\,\,1\,\,{\text{yar}}{{\text{d}}^2}\]
\[\left( {{\text{carpet}}} \right)\,\,xy\,\,{\text{f}}{{\text{t}}^2}\,\,\,\, \leftrightarrow \,\,\,\$ 50\]
\[\left( {{\text{carpet}}} \right)\,\,\,\,\frac{{\$ \,\,\,?}}{{1\,\,\,{\text{yar}}{{\text{d}}^2}\,\,}}\,\,\,\,\,\]
\[?\,\, = \,\,\,\left( {\frac{{\$ 50}}{{xy\,\,{\text{f}}{{\text{t}}^2}}}\begin{array}{*{20}{c}}
\nearrow \\
\nearrow
\end{array}} \right)\,\,\,\left( {\frac{{9\,\,{\text{f}}{{\text{t}}^2}}}{{1\,\,{\text{yar}}{{\text{d}}^2}}}\begin{array}{*{20}{c}}
\nearrow \\
\nearrow
\end{array}} \right)\,\,\,\, = \,\,\,\,\frac{{\$ \,\,450}}{{xy\,\,{\text{yar}}{{\text{d}}^2}\,}}\,\,\,\,\mathop = \limits^{{\text{FOCUS}}!} \,\,\,\,\frac{{\$ \left( {\frac{{450}}{{xy}}} \right)}}{{1\,\,{\text{yar}}{{\text{d}}^2}\,\,}}\]
Obs.: arrows indicate
licit converters.
This solution follows the notations and rationale taught in the GMATH method.
Regards,
Fabio.
