Question

How do you find the area of a circle?

How do you find the circumference of a circle?
What information do you need in order to find the area or circumference of a circle?
To determine the number of full rotations your tires complete before you need to switch the front and back tires, will you be working with area or circumference?

Answer 1

Area is pi * (radius^2)
Circumference is pi * diameter
The infirmation you'll need is either a radius or diameter. Diameter is twice the radius.
For question four, you will be working with circumference.