Now it's quite likely that next time I come we can spend quite a bit of time doing this same thing again yeah cos there's a lot in it there's angles using a protractor adding things up to check they come to the total that the angles come to three sixty and there's this thing about fractions there's cancelling fractions and then there's working with quite big numbers three hundred and sixty what's two fifteenths of three hundred and sixty mm that's quite hard.