BTGmoderatorLU wrote:Source: Veritas Prep
An animal shelter began the day Tuesday with a ratio of 5 cats for every 11 dogs. If no new animals arrived at the shelter, and the only animals that left the shelter were those that were adopted, what was the ratio of cats to dogs at the end of the day Tuesday?
(1) No cats were adopted on Tuesday.
(2) 4 dogs were adopted on Tuesday.
\[\begin{array}{*{20}{c}}
{{\text{cats}} = \,\,5\,k} \\
{{\text{dogs}} = 11\,k}
\end{array}\,\,\,\,\,\,\left( {k > 0\,\,\,\operatorname{int} } \right)\,\,\,\,\,\,\,\left( * \right)\]
\[\left( * \right)\,\,k\,\, = \,\,11k - 2\left( {5k} \right)\,\,\,{\text{ = }}\,\,\,{\text{difference}}\,\,{\text{of}}\,\,{\text{ints}}\]
That´s the
k technique, a "killer" tool of our method (when dealing with ratios)!
\[\left( {1 + 2} \right)\,\,\,\,\,{\text{?}}\,\,\, = \,\,\,\frac{{5k}}{{\,11k - 4\,}}\,\,\,\,\, \Rightarrow \,\,\,\,\,\left\{ \begin{gathered}
\,{\text{Take}}\,\,k = 1\,\,\,\, \Rightarrow \,\,\,? = \frac{5}{7} \hfill \\
{\text{Take}}\,\,k = 2\,\,\,\, \Rightarrow \,\,\,? = \frac{{10}}{{18}} \ne \frac{5}{7} \hfill \\
\end{gathered} \right.\]
The above follows the notations and rationale taught in the GMATH method.