Semi-circle "Circumference"

Semi-circle circumference

What is the perimeter of this shape‌

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 . 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.

 

Example 1
What is the perimeter of this shape‌
Step 1: Find the circumference of the full circle.

 

Step 2: Divide the circumference in half.

 

 

 

 

Step 3: Add the diameter.
12.56 + 8 = 20.56 cm
This is the perimeter of the semi-circle!

 

 

Example 2
Find the perimeter of this quarter circle.

 

 

 

Example 3
A wire is bent to form three semicircles. Find the length of the wire in terms of .

 

 

 

Semi-circle circumference – CLASS PRACTICE

Solve each of the following problems.

Find the perimeter of this shape. Find the perimeter of this shape.
A garden is in the shape of a quarter circle. Find its perimeter. A circle is drawn inside a square. Find the circumference of the circle.

A rope is arranged to form two semi-circles as shown. Find the length of the rope in terms of ¹.
   
               

 

 

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