Question: Why was the area upset with the perimeter?
Answer: Because the area thought the perimeter always went around the problem.
Perimeter is the total distance taken up around the outside of a shape.
Can you think of examples of where perimeter might be used?
A good example is if you are fencing a field, or building a wall around something. You will need to know the perimeter.
To find the perimeter simply add up all the lengths of each shape.
When you have a missing length, such as in this example, break it down as shown above.
Perimeter = 10 + 2 + 6 + 6 + 4 + 8 = 36 cm
Calculate the missing length. If the slant height isn't given, you have to assume it is 4 cm.
Perimeter = 4 + 10 + 10 = 24 cm
The length of the semicircle can be calculated by finding the circumference and dividing by 2.
Circumference = π x diameter
The circumference of the circle is π x 12 = 37.70 cm (Take the value of pi as 3.142)
To get the circumference of the semicircle: 37.70 ÷ 2 = 18.85 cm
The missing length of the rectangle is 11 cm
12 + 11 + 11 + 18.85 = 52.85 cm
Let's move on to some questions now.