If the coordinates of the mid points of the sides PQ and QR of ΔPQR are (-1, 8) and (2, 4) respectively, then length of PR is :

10

Let us consider that mid point of PQ is X and mid point of QR is Y.

Length of PR = 2 × length of XY

Length of XY = \(\sqrt { ( x2 - x1 )² + ( y2 - y1 )² }\)

= \(\sqrt { ( 2 -(-1) )² + ( 4 - 8 )² }\)

= \(\sqrt { 9 + 16 }\)

= \(\sqrt { 25 }\) 5

So, length of PR = 2 × 5 = 10

The correct answer is option (2) : 10