The Chief Examiner reported that majority of the candidate who attempted this question performed poorly. According to the report, their performance indicated that majority of the candidates had poor understanding of position vectors.
In part (a), candidates were expected to show that if P,Q and R lie in the same straight line, then gradient of PQ = gradient of QR.Gradient of PQ = =. Gradient of QR =. Since both gradients were the same, it implied that the points P,Q and R were collinear.

In part (b), candidates were expected to respond as follows:
.  
|| =  =
Therefore   : =  = 2:1.