Question

Which of the following formulas is used to find the circumference of a circle?

Answer 1

D. C = 2πr

Explanation:

The formula to find the circumference of the circle is:

2 · π · radius

So, the answer is D. C = 2πr

Answer 2

`\textsf{D.}\quad C = 2\pi r`

Explanation:

π is a mathematical constant representing the ratio of a circle's circumference (C) to its diameter (d):

`\pi = (C)/(d)`

The diameter (d) of a circle is twice the length of the circle's radius (r), so d = 2r. Therefore the ratio can be written as:

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

Multiply both sides of the equation by 2r to isolate C:

`\begin{aligned}\pi\cdot 2r& = (C)/(2r)\cdot 2r\\\\2\pi r&=C\\\\C&=2\pi r\end{aligned}`

Therefore, the formula used to find the circumference of a circle is:

`\large\boxed{C=2\pi r}`