Since Q is to the West of P and R is to the South of P, the positions of Q, P, and R form a right-angled triangle with the right angle at P. The distance PQ is one leg (60 km) and PR is the other leg (80 km). The distance between Q and R is the hypotenuse of this right-angled triangle. Using the Pythagorean theorem (a^2 + b^2 = c^2), the distance QR is sqrt(60^2 + 80^2) = sqrt(3600 + 6400) = sqrt(10000) = 100 km.