Question

Circumference C of a circle can be found by multiplying diameter d with ___.

Answer 1

Understand that for a circle whose radius $r$ and diameter $d$are related as:

$\begin{array}{l}r=\frac{d}{2}\\ \Rightarrow d=2r\end{array}$

And the circumference C of a circle having radius $r$ is given as $2\pi r$.

Therefore,

$\begin{array}{l}C=2\pi r\\ \Rightarrow C=\pi d\end{array}$

Hence,Circumference C of a circle can be found by multiplying diameter d with $\pi$.