A man walks 40 metres towards the south. Then turning to his right he walks 40 metres. Then he turns to his left and walks 20 metres. He again turns to his left and walks 40 metres. How far is the man now from his starting point?

The man is 60 metres from his start.

From (0, 0), 40 m south gives (0, -40).

A right turn faces west; 40 m gives (-40, -40).

Left to south, 20 m gives (-40, -60); left to east, 40 m gives (0, -60).

Distance = root(0^2 + 60^2) = 60 metres.