# What is the circumference of a 15-inch circle if the diameter of a circle is directly proportional to its radius and a circle with a 2-inch diameter has a circumference of approximately 6.28 inches?

##### 1 Answer

I believe the first part of the question was supposed to say that the circumference of a circle is directly proportional to its diameter. That relationship is how we get

This corresponds to the formulas for determining the circumference of a circle, which are *pi* .