Question

If A(3, 5), B(– 5, – 4), C(7, 10) are the vertices of a parallelogram taken in order, then the co-ordinates of the fourth vertex are:

(a) (10, 12) 

(b) (12, 17) 

(c) (15, 19) 

(d) (18, 21)

Answer 1

(c) (15, 19)

Let Δ(a, b) be the fourth vertex of the parallelogram ABCD. The diagonals of a parallelogram bisect each other at point O (say), so the diagonals AC and BD have the same mid-point.