The Sum of the measures of the exterior angles of a polygon is 360°.
Proof:
1. Draw a polygon (a pentagon ABCDE as shown in figure) on the floor
using a piece of chalk.
2. Start walking from A. Walk along AB on reaching B, you need to turn
through an angle of m∠1 to walk along BC. On reaching C, you
must turn through an angle of m∠2 to walk along CD.
3. Continue moving in the same manner,until you return to the side AB.
4. You will find that you have made one complete turn.