The circumference of a circle is equal to 72 pi. Find the radius of this circle.
Choices:  A) 35  B) 36  C) 37  D) 38  E) 39
The circumference of a circle is given by   C = 2 pi r, where r is the radius of the circle.   Substitute C by 72 pi to obtain the equation   72 pi = 2 pi r   Simplify and solve for r to obtain   r = 36   Answer 36
<result>B</result>
The circumference of a circle is equal to 72 pi. Find the radius of this circle.