Question

The area of a circle is 100 square millimeters. What is the circumference?

Answer 1

`\begin{gathered} Area\text{ of circle = }\pi r^2 \\ 100=3.14r^2 \\ r^2=(100)/(3.14) \\ r^2=31.85 \\ r=\sqrt[]{31.85} \\ r=5.64\text{ mm} \end{gathered}`
`\begin{gathered} \text{The circumference of a circle = 2}\pi r \\ =\text{ 2 x 3.14 x 5.64} \\ =35.42\text{ mm }\cong35.4\text{ mm (1 decimal place)} \end{gathered}`