Video and Examples
Finding the perimeter of semi-circles using the formula 
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What is the perimeter of a semi-circle with a diameter of 8cm? |
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To answer this question, we need to realize that the figure is just half of a circle. This means we will still be using the formula 
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However, there will be a twist in what we do, because the formula 
gives us the circumference of a complete circle.
You will solve this problem using three steps: find the circumference of a full circle with the same diameter, divide that circumference in half, and then add the diameter.
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Example 1 What is the perimeter of a semi-circle with a diameter of 8cm? |
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Step 1: Find the circumference of the full circle.
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Step 2: Divide the circumference in half.
This is the length of just the curvy part of the semi-circle. |
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Step 3: Add the diameter. 12.56 + 8 = 20.56 cm This is the perimeter of the semi-circle! |
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Example 2 Find the perimeter of this quarter circle.
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Example 3 A wire is bent to form three semicircles. Find the length of the wire in terms of
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Semi-circle circumference – CLASSWORK
Solve each of the following problems.
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Find the perimeter of this shape. |
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Find the perimeter of this shape. |
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Self-Check
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Question 1
A rope is arranged to form two semi-circles as shown. Find the length of the rope in terms of π.
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[show answer] |
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Question 2 A garden is in the shape of a quarter circle. Find its perimeter.
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[show answer] |
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Question 3 A circle is drawn inside a square. Find the circumference of the circle.
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[show answer] |
