Question
Find the position vector of a point R which divides the line joining two points P and Q whose position vectors are 
and 
respectively, in the ratio 2 : 1
(i) internally (ii) externally
Solution
Let 
and 
be position vectors of P and Q respectively.
(i) The position vector of the point R dividing the join of P and Q internally in the ratio 2 : 1 is
i.e.. 
(ii) The position vector of the point R dividing the join of P and Q externally in the ratio 2 : 1 i.e.. internally in the ratio 2 : – 1 is 
