fskilnik@GMATH wrote:GMATH practice exercise (Quant Class 15)
If ABCD is a rectangle, what is the value of y+z ?
(1) x = 40
(2) M is the midpoint of line segment BC, and N is the midpoint of line segment CD
Obs.: all angles are measured in degrees.
$$\left( {{\rm{Vertex}}\,A\,,\,\,{\rm{see}}\,\,{\rm{first}}\,\,{\rm{figure}}} \right)\,\,\,\,\,\left( {90 - y} \right) + x + \left( {90 - z} \right) = 90\,\,\,\,\, \Rightarrow \,\,\,\,\,\,y + z = x + 90\,\,\,\,\,\left( * \right)$$
$$? = y + z\,\,\,\,\,\mathop \Leftrightarrow \limits^{\left( * \right)} \,\,\,\,\,\boxed{\,? = x\,}$$
$$\left( 1 \right)\,\,\,x = 40\,\,\,\,\, \Rightarrow \,\,\,\,\,\,{\text{SUFF}}.$$
$$\left( 2 \right)\,\,{\rm{INSUFF}}.\,\,\,:\,\,\,{\rm{geometric}}\,\,{\rm{bifurcation}}\,\,\left( {{\rm{see}}\,\,{\rm{images}}} \right)$$
The correct answer is (A).
We follow the notations and rationale taught in the GMATH method.
Regards,
Fabio.