Question

A has a circumference of 10 inches. Find its approximate radius, diameter and area

Answer 1

ANSWER

• r = 5/π in

,

• D = 10/π in

,

• A = 25/π in²

EXPLANATION

The circumference of a circle is:

$C=2\pi r$

So if we know that the circumference is 10 inches we can find the radius:

$\begin{gathered} 10=2\pi\cdot r \\ r=\frac{10}{2\pi}=\frac{5}{\pi} \end{gathered}$

The diameter is twice the radius:

$D=2r=2\cdot\frac{5}{\pi}=\frac{10}{\pi}in$

And the area of a circle is:

$A=\pi r^2=\pi\cdot(\frac{5}{\pi})^2=\pi\cdot\frac{25}{\pi^2}=\frac{25}{\pi}in^2$