a70
If p and q are positive integers, is q odd?
(1) 2p+3q=12
(2) 4p/5q is an odd integer
\(p,q\,\, \ge 1\,\,{\rm{ints}}\,\,\,\left( * \right)\)
\(q\,\,\mathop = \limits^? \,\,{\rm{odd}}\)
\(\left( 1 \right)\,\,\,2p + 3q = 12\,\,\,\,\,\mathop \Rightarrow \limits^{\left( {**} \right)} \,\,\,\,\left\langle {{\rm{NO}}} \right\rangle\)
\(\left( {**} \right)\,\,q\,\,{\rm{odd}}\,\,\,\mathop \Rightarrow \limits^{\left( * \right)} \,\,\,\,\left( {12 = } \right)\,\,2p + 3q\,\,{\rm{odd}}\,\,{\rm{,}}\,\,\,{\rm{impossible}}\)
\(\left( 2 \right)\,\,\,{{4p} \over {5q}} = {\rm{odd}}\,\,\,\,\, \Rightarrow \,\,\,4p = 5q \cdot {\rm{odd}}\,\,\,\,\,\mathop \Rightarrow \limits^{\left( {***} \right)} \,\,\,\,\left\langle {{\rm{NO}}} \right\rangle\)
\(\left( {***} \right)\,\,\,q\,\,{\rm{odd}}\,\,\,\mathop \Rightarrow \limits^{\left( * \right)} \,\,\,\,\,\left( {4p = } \right)\,\,5q \cdot {\rm{odd}}\,\,{\rm{ = }}\,\,{\rm{odd}}\,\,{\rm{,}}\,\,\,{\rm{impossible}}\,\)
The correct answer is therefore (D).
This solution follows the notations and rationale taught in the GMATH method.
Regards,
Fabio.