Question

What is the area of semicircle of radius 3r​

Answer 1

$area \: of \: the \: semi \: circle \: of radius \: 3r \: \\ = \frac{\pi \times \ \: 3 \ r2}{2}$

Answer 2

The area of a semicircle of radius 3r is $\displaystyle \sf{ } \frac{9}{2} \pi {r}^{2}$

Given :

A semicircle of radius 3r

To find :

The area of the semicircle

Formula :

The area of a semicircle of radius r

$\displaystyle \sf{ } = \frac{1}{2} \pi {r}^{2}$

Solution :

Step 1 of 2 :

Write down the radius of the semicircle

Here it is given that semicircle of radius 3r

Step 2 of 2 :

Find area of the semicircle

The area of the semicircle

$\displaystyle \sf{ } = \frac{1}{2} \pi {(3r)}^{2}$

$\displaystyle \sf{ } = \frac{1}{2} \times \pi \times 9 {r}^{2}$

$\displaystyle \sf{ } = \frac{9}{2} \pi \times {r}^{2}$

$\displaystyle \sf{ } = \frac{9}{2} \pi {r}^{2}$