SOLUTION: In the diagram, three vertices of parallelogram ORST are O(0, 0), R(b, d), and T(a,0). What are the coordinates of S? 1. (a, b) 2. (a, d) 3. (a + b, d) 4. (a + b, b)

Since T is a units to the right of O, then S must be a units to the
right of R.  R is b units to the right of the y-axis, so S must be
a more units to the right of the y-axis than R is, so S's x-coordinate
must be a more than R's x-coordinate, so we add b to R's x-coordinate
and get that S's x-coordinate is b+a.  Also S must be the same distance
above the x-axis as R is.  R is d units above the x-axis, so S's 
y-coordinate must be the same as R's y-coordinate, d.  So the coordinates
of point S are S(b+a,d).



Since b+a is the same as a+b, the correct choice is 3.

Edwin