The perimeter of the outside of the running track is the sum of the lengths A, B, C, and D.
Notice that A=B=100 yd, and D=C.
To find D we compute the semi perimeter of a circle with radius:
[tex]r_D=\frac{40yd}{2}+10yd=30yd\text{.}[/tex]
Then:
[tex]D=\frac{1}{2}\pi\cdot2r_D=\pi r_D=30\pi yd\text{.}[/tex]
Therefore the perimeter of the outside of the running track is:
[tex]A+B+C+D=(60\pi+200)yd\text{.}[/tex]
Answer: 388.5yd.
