# The circle

## The perimeter of a semicircle

Remember that the is the distance round the outside.

A semicircle has two edges. One is half of a circumference and the other is a diameter.

$C = \pi d$

$= 3.14 \times 8$

$= 25.12cm$

Remember this is the circumference of the whole circle, so now we need to half this answer.

$25.12 \div 2 = 12.56cm$

Total perimeter $$= 12.56 + 8 = 20.56cm$$

## Area of a circle

For any circle with radius, r, the area, A, is found using the formula:

$A = \pi {r^2}$

$A = \pi {r^2}$

$= 3.14 \times 12 \times 12$

$= 452.16c{m^2}$

## The area of a semicircle

A semicircle is just half of a circle. To find the of a semicircle we calculate the area of the whole circle and then half the answer.

$A = \pi {r^2}$

$= 3.14 \times 4 \times 4$

$= 50.24c{m^2}$

Area of semicircle $$= 50.24 \div 2 = 25.12c{m^2}$$

## The area of a combined shape

This shape is made up of a rectangle and a semicircle.

To find the total area we just find the area of each part and add them together.

Area of the rectangle = length x breadth

$= 20 \times 30$

$= 600m{m^2}$

$Area\,of\,circle = \pi {r^2}$

$= 3.14 \times 10 \times 10$

$= 314m{m^2}$

$Area\,of\,semicircle = 314 \div 2 = 157m{m^2}$

$Total\,area = 600 + 157$

$= 757m{m^2}$