Question

find the length of the radius if the circumference is 13.2 round to one decimal place. use 3.14 for π

Answer 1

Given

$\begin{gathered} \text{Circumference of Circle = 13.2 unit} \\ \pi\text{ = 3.14} \end{gathered}$

Required :

$\text{length of radius (r) = ?}$

The formula for the circumference of a circle:

$\text{Circumference of circle = 2}\pi r$

When we substitute and simplify:

$\begin{gathered} 13.2\text{ = 2 }\times\text{ }\pi\text{ }\times\text{ r} \\ \text{making r the subject of formula} \\ r\text{ = }\frac{13.2}{2\text{ }\times\text{ 3.14}} \\ r\text{ = 2.1019} \\ \approx\text{ 2.1 unit (1.d.p)} \end{gathered}$