Question

question 1 of 10
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 = πrd
b. c = 2πd
c. c = πd
d. c = πd²

Explanation:

Step1: Recall the relationship between radius and diameter

The diameter $d$ of a circle is related to the radius $r$ by the formula $d = 2r$.

Step2: Substitute $d = 2r$ into the circumference formula

Given $C=2\pi r$, and since $d = 2r$, we can substitute $2r$ with $d$ in the formula for the circumference. So $C=\pi d$.

Answer:

C. $C = \pi d$