well, we know a circle has a total of 360°, now, if we divide 360 by 60, we get 360/60 = 6, namely 60° + 60° + 60° + 60° + 60° + 60° = 360°, well that just means that 60° is 1/6 of whole circle.
we know the circle has a total of 42π, how much is 1/6th of that? [tex]\bf \cfrac{1}{6}\cdot 42\pi \implies 7\pi \approx 22[/tex]