P, Q and R are three towns. The distance between P and Q is 60 km, whereas the distance between P and R is 80 km. Q is in the West of P and R is in the South of P. What is the distance between Q and R?

Correct Option: 100 km

According to the problem statement, P, Q, and R are three towns. Distance between P and Q is 60 km, and Q is to the West of P. Distance between P and R is 80 km, and R is to the South of P. Since Q is West of P and R is South of P, the directions form a right-angled triangle PQR at vertex P. The distance PQ = 60 km and PR = 80 km. The distance between Q and R is the hypotenuse QR. Using Pythagoras theorem: QR squared = (PQ squared) + (PR squared) => QR squared = (60 squared) + (80 squared) => QR squared = 3600 + 6400 = 10000. Therefore, QR = square root of 10000 = 100 km. Hence, the correct option is 100 km.