Circumference of a circle is defined as which of the following?

• A. Distance across the circle
• B. Distance around the circle
• C. Radius length
• D. Area inside the circle

Answer: (B)

Circumference is the length of the circle's boundary—the distance you would travel if you went all the way around the circle. This is the outer edge, or perimeter, of the circle. It’s different from the distance across the circle, which is the diameter; the radius is the distance from the center to the edge; and the area is the space inside the circle. In formulas, circumference relates to radius by C = 2πr (or to diameter by C = πd).