Lets get started :)
The circumference formula of a circle is
C = 2[tex] \pi [/tex]r (r being the radius)
If radius = 45, substitute 45 instead of r
C = 2 [tex] \pi [/tex](45)
=90[tex] \pi [/tex]
≈ 282.7433388
I suppose you leave it in the pi ([tex] \pi [/tex]) form
