Question

Given that P (3, 2, – 4), Q (5, 4, –6) and R (9, 8, –10) are collinear. Find the ratio in which Q divides PR.

Answer 1

Let point Q (5, 4, –6) divide the line segment joining points P (3, 2, –4) and R (9, 8, – 10) in the ratio k:1.
Therefore,

 by section formula,

Thus, point Q divides PR in the ratio 1:2.