This question looks pretty familiar...
Let's use where C = circumfrence and r = radius.
Because the diameter = 2 × the radius, we can use this instead:
[tex]C=\pi d[/tex]
Plug in 170,000 for d (our diameter).
[tex}C = \pi\times170,000[/tex]
If you want an exact answer, use 170,000[tex]\pi[tex].
If you want a decimal, just plug that into your calculator