Circumference of a circle is given by which formula?

Circumference of a circle is given by which formula?

• A. C = π d
• B. C = π r
• C. C = 2π r
• D. C = r²

Answer: (C)

Circumference depends on the circle’s size through π. The way to write it most directly uses the radius: C = 2πr. This comes from the fact that the diameter is twice the radius, and the formula with diameter is C = πd. Substituting d = 2r gives C = 2πr. So this form is the standard one to memorize when the radius is given. You can also use the diameter form, C = πd, which is equivalent. The option C = πr would give only half the circumference, and C = r² is not a circumference at all but an area.

Circumference depends on the circle’s size through π. The way to write it most directly uses the radius: C = 2πr. This comes from the fact that the diameter is twice the radius, and the formula with diameter is C = πd. Substituting d = 2r gives C = 2πr. So this form is the standard one to memorize when the radius is given. You can also use the diameter form, C = πd, which is equivalent. The option C = πr would give only half the circumference, and C = r² is not a circumference at all but an area.