In △PQR,
PR2=PQ2+QR2 (By Pythagoras theorem)
⇒PR2=122+52
⇒PR2=144+25
⇒PR2=132
⇒PR=13
In a right angled triangle, the length of the median on its hypotenuse is half the length of the hypotenuse.
∴l(QS)=12(PR)=12(13)
= 6.5 units.
Hence, the length of QR is 6.5 units.