Question

I need to equation for the radius of a 400m running track I know the answer is 36.5 and I know the formula is =2$\pi$r

Answer 1

This formula only applies if the track is circular.  If it is, then we write the equation:

2*r*pi=400

Dividing by 2pi, we see that:

r=200/pi

This is approximately 63.66.