A man's house faces south. From the front door he walks 20 metres straight, turns left and walks 50 metres, then turns right and walks 80 metres and stops. Find the distance from the point where he stops to the front door of his house.

The distance is 50 root 5 metres.

Place the door at origin, facing south walk 20 m south.

Turn left (east) 50 m, then right (south) 80 m.

Net displacement: 50 m east and 20 + 80 = 100 m south.

Distance = root(50^2 + 100^2) = root(12500) = 50 root 5 m.