Question

If r is the radius of a circle and d is its diameter, which of the following is an equivalent formula for the circumference C=2πr?

A. C=2πd
B. C=πD
C. C=πr2
D. C=πdr

Answer 1

The answer is B. C=πD

Answer 2

Option B is correct

C=πD

Explanation:

As per the statement:

If r is the radius of a circle and D is its diameter.

Given the circumference of the circle:

`C = 2 \pi r` .....[1]

where,

r is the radius of the circle.

We know that:

diameter(D) = 2r

Substitute in [1] we have;

`C = \pi (2r) = \pi D`

Therefore, the equivalent formula for the circumference C=2πr is, C=πD