Area of a semicircle. Finding the area of semi circles.
Area of a semicircle video
To find the area of a semicircle first you need to find the
area of the whole circle and divide your answer by 2, as a semicircle takes up
half the space of a circle.
To find the area of the circle use A=π×r2. (A stands for the area of the circle, π is Pi and r is the radius of the circle).
Let’s take a look at an example.
Find the area of this semicircle.
First find the area of the whole circle. Make sure that you use the radius of the circle (the distance halfway across the circle), this is 4 cm as the diameter is 8 cm (the distance all the way across the centre of the circle).
A = π×r2
A= 50.3... cm2
Now all you need to do is divide the answer by 2
50.3... ÷ 2 = 25.1 cm2 (1 d.p)
A semicircular shaped doormat has a radius of 7cm. Calculate the area of the doormat.
To begin with first find the area of the circle by using A = π×r2.
A = π×r2
A= 154.1... cm2
Again, all you need to do now is to divide the area of the circle by 2.
Do this by 154.1 ÷ 2 = 77.1 cm2 (1 d.p)
If you don’t have a scientific calculator then use Pi as 3.14 on your pocket calculator.
As you do more examples you might just want to use the formula A = π×r2/2. This will means less lines of working out.
More by this Author
A compound shape is a shape that is made up from other simple shapes. In this article we will be working out the area of a L shape (made up from 2 rectangles). To find the area of a compound shape, follow these simple...
The density, mass and volume triangle is as follows: So if you wanted to work out the density, you would cover up density in the magic triangle to give: Density = Mass/Volume (since mass is above volume) So if...
The surface area of a triangular prism can be found in the same way as any other type of prism. All you need to do is calculate the total area of all of the faces. A triangular prism has 5 faces, 3 being rectangular and...