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Area of a semicircle. Finding the area of semi circles.

Updated on March 01, 2013

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.

Example 1

Find the area of this semicircle.

Answer

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= π×42

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)

Example 2

A semicircular shaped doormat has a radius of 7cm. Calculate the area of the doormat.

Answer

To begin with first find the area of the circle by using A = π×r2.

A = π×r2

A= π×72

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)

Extra Tips

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.


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    Yomama 3 years ago

    thanks broham

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    travis 4 years ago

    thank you so much, it helped me with my homework

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    andrea 4 years ago

    Thank this really helped me on my math homework

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    Palm 4 years ago

    Lovely jubbly thanks a bunch

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    Mikah 4 years ago

    I still don't understand this I am only 10 but my teacher has said that this is a question that is going to appear in my exam I don't understand what all the tt things mean sorry

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    Amana 5 years ago

    THANKS SO MUCH NOW I CAN ANWSER THE QUESTION ON MY MATH TEST TOMORROW! EVERYBODY SAID IT WAS HARD!!!!!!!!! BUT ILL PRON=BABLY DO GOOD NOW !!!! THANKS A BUNCH!

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    Daniel 5 years ago

    fantastic that is absolutly nice thanks

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    Chubby cuteness 5 years ago

    Really good thank you so much I am so grateful

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    Rizza 5 years ago

    Thanks Very easy to understand. Awesome

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    Johnson 6 years ago

    Nice

    I Like it

    Guess what

    Geometry is also cool

    Even my dog understands this

    Really helpful thnx!

    See ya

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    dd 6 years ago

    thanx you really helped me ace my test

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    shaz 6 years ago

    fantastic very useful thanks.

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    Soph 6 years ago

    Thanks, this really helped me answer a question in an exam paper :)

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    (: 6 years ago

    thank you, this really does help :D

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    Author

    Mark 6 years ago from England, UK

    Thanks for your nice comments.

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    maths teacher  6 years ago

    this is very useful thants

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    :) 6 years ago

    Thanks, ;) simple and easy to understand as always, just hope it comes up in my exam =(

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    koyasha bridges 6 years ago

    thank you so much

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    marco  7 years ago

    thx this was helpful as my mate gave me the wrong note i would of failed if it weren't for this website i love u moderator :P

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    niv 7 years ago

    this was really simple and easy to understand, thanks

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