Question

The position vectors of the vertices P, Q, and R of a triangle PQR are (-1, 2, 4), (3, 6, 8), and (11, 1, 2) respectively. Which of the following vectors represents the median PS?
1) (-1, 4, 6)
2) (3, 4, 6)
3) (6, 4, 6)
4) (7, 4, 6)