Which formula represents the circumference of a circle?

Which formula represents the circumference of a circle?

• A. C=2πr
• B. A=πr^2
• C. A=1/2 bh
• D. y = mx + b

Answer: (A)

Circumference is the distance around a circle. It scales with the circle’s size, and the relationship uses the radius because the diameter is twice the radius, and the circle’s edge corresponds to that distance around. The correct formula is C = 2πr, since multiplying the radius by 2 gives the diameter and matching it with π converts a straight distance around the circle. For example, if the radius is 3 units, the circumference is 2π(3) = 6π units. The other expressions describe different things: πr^2 is the area of a circle, 1/2 bh is the area of a triangle, and y = mx + b is the equation of a straight line.

Circumference is the distance around a circle. It scales with the circle’s size, and the relationship uses the radius because the diameter is twice the radius, and the circle’s edge corresponds to that distance around. The correct formula is C = 2πr, since multiplying the radius by 2 gives the diameter and matching it with π converts a straight distance around the circle. For example, if the radius is 3 units, the circumference is 2π(3) = 6π units. The other expressions describe different things: πr^2 is the area of a circle, 1/2 bh is the area of a triangle, and y = mx + b is the equation of a straight line.