The heptagon is another irregular shape, having an odd number of sides but despite this it is a shape that we come across on a daily basis:




The British 50p coin, and also the British 20p coin are both examples of “heptagonal” shapes.  Once again you can see that the external angles will also add up to 360° although in this particular case I rounded it down to 51.4° and if you multiply this by seven you come up with 359.8° which, within the remit of common sense is of course 360° when you take into account the rounding that I did.