AkshdeepS wrote:

The Lewiston Road Race is how many kilometers long?

(1) It takes 2 more hours to complete the race at an average speed of 40 kilometers per hour than at an average speed of 50 kilometers per hour.

(2) At an average speed of 20 kilometers per hour, it took Brett 10 hours to complete half the race.

\(? = D\,\,\,\,\,\left[ {{\rm{km}}} \right]\)

Let´s use

UNITS CONTROL, one of the most powerful tools of our method!

\(\left( 1 \right)\,\,\,\left( {\,\,\left[ {{\rm{km}}} \right] \cdot {{\left[ {\rm{h}} \right]} \over {\left[ {{\rm{km}}} \right]}}\,\, = \,\,\left[ {\rm{h}} \right]\,} \right)\,\,\,\,\,\, \Rightarrow \,\,\,\,\,\,D \cdot {1 \over {40}} - D \cdot {1 \over {50}} = 2\,\,\,\,\left[ {\rm{h}} \right]\,\,\,\,\,\,\,\, \Rightarrow \,\,\,\,\,\,\,{\rm{SUFF}}.\,\,\,\,\,\,\,\,\,\left( {{1^{{\rm{st}}}}\,\,{\rm{degree}}\,\,{\rm{equation}}\,\,{\rm{in}}\,\,D} \right)\)

\(\left( 2 \right)\,\,\,?\,\, = \,\,2 \cdot 10\,{\rm{h}}\,\, \cdot \,\,{{20\,\,{\rm{km}}} \over {1\,\,{\rm{h}}}}\,\, = 400\,\,\,\,\left[ {\,{\rm{km}}\,} \right]\,\,\,\,\,\,\, \Rightarrow \,\,\,\,\,\,\,{\rm{SUFF}}.\,\)

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

Regards,

Fabio.

_________________

Fabio Skilnik :: https://GMATH.net (Math for the GMAT) or GMATH.com.br (Portuguese version)

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