BTGmoderatorDC wrote:If s and t are two different numbers on the number line, is s + t = 0 ?
(1) Distance between s and 0 is the same as distance between t and 0
(2) 0 is between s and t
Source: GMAT Prep
$$s \ne t\,\,\,\,\left( * \right)$$
$$s + t\,\,\mathop = \limits^? \,\,0$$
$$\left( 1 \right)\,\,\,\left| s \right| = \left| t \right|\,\,\,\,\mathop \Rightarrow \limits^{\left( * \right)} \,\,\,\,s = - t\,\,\,\,\, \Rightarrow \,\,\,\,\,\left\langle {{\rm{YES}}} \right\rangle $$
$$\left( 2 \right)\,\,\,st < 0\,\,\,\,\left\{ \matrix{
\,{\rm{Take}}\,\,\left( {s,t} \right) = \left( { - 1,1} \right)\,\,\,\, \Rightarrow \,\,\,\,\left\langle {{\rm{YES}}} \right\rangle \hfill \cr
\,{\rm{Take}}\,\,\left( {s,t} \right) = \left( { - 1,0.5} \right)\,\,\,\, \Rightarrow \,\,\,\,\left\langle {{\rm{NO}}} \right\rangle \hfill \cr} \right.$$
This solution follows the notations and rationale taught in the GMATH method.
Regards,
Fabio.