A circle has diameter 6. What is its circumference?

A circle has diameter 6. What is its circumference?

• A. 3π
• B. 12π
• C. 9π
• D. 6π

Answer: (D)

Circumference is the distance around a circle. It’s found using C = πd or, equivalently, C = 2πr. With a diameter of 6, the radius is 3, so C = 2πr = 2π×3 = 6π. Using C = πd gives C = π×6 = 6π as well. So the circumference is 6π. The other options would correspond to using a different radius or a mistaken relation, but for a circle with diameter 6, 6π is the correct value.

Circumference is the distance around a circle. It’s found using C = πd or, equivalently, C = 2πr. With a diameter of 6, the radius is 3, so C = 2πr = 2π×3 = 6π. Using C = πd gives C = π×6 = 6π as well. So the circumference is 6π. The other options would correspond to using a different radius or a mistaken relation, but for a circle with diameter 6, 6π is the correct value.