Here's a solution to a problem I thought of:

How fast does the Sun travel around the Galaxy (Milky Way)?

Find: v
Given: Distance from Center of Galaxy to Sun, r(CS)=2.5E17 km
Period of rotation of Sun around Galaxy, t=2.5E8 y

s=2(pi)r(CS)=2(pi)(2.5E17 km)=1.57E18 km
t=2.5E8 y x 365 d/y x 24 h/d = 2.19E12 h
v=s/t=1.57E18 km / 2.19E12 h = 717 258.6 km/h

So there you have it!