Dana is planning to ride her bicycle around the circular race track and
wants to know the distance. If the diameter of the track is 2 mile, how far is the distance
around the race track?

Question

Dana is planning to ride her bicycle around the circular race track and 
wants to know the distance.  If the diameter of the track is 2 mile, how far is the distance 
around the race track?

4n1m0s1ty · Answer

Its a circular race track, so the distance must be the circumference:

C = 2*pi*r where r = diameter/2

Can you solve it now?

directrix · Answer

From above ^^ C = 2*pi*r. 
Twice the radius is the diameter so you could think about the problem as having formula 
C = pi*d where d = 2 miles . So, the circumference (distance around the track) is ?