Madhya Pradesh Police Exam Model Paper 3

Given:
The perimeter of a semi-circle is 72cm
Concept Used:
The perimeter of the semi-circle is (πr + 2r) where r is the radius of the semi-circle
Diameter = 2 × radius
Calculation:Perimeter of the semi-circle is 72cm
$\left(\mathit{\pi }\mathit{r}+2\mathit{r}\right)=72$
$\Rightarrow \mathit{r}\left(\mathit{\pi }+2\right)=72$
$\Rightarrow \mathit{r}\left(22/7+2\right)=72$
$\Rightarrow \mathit{r}\left(36/7\right)=72$
$\Rightarrow \mathit{r}=72\times 7/36$
$\Rightarrow \mathit{r}=14$
Radius of the semi-circle is 14cm
Diameter = 2 × 14cm
⇒ 28cm
∴ The diameter of the semi-circle is 28cm