Perimeter

1
Perimeter Area

• By Heather Parent

2
Reminders

• What Does The Dictionary Say?
• What is the Perimeter of a polygon?
• What is the Area of a polygon?
• What about Circles?
• A circle doesnt have a perimeter, it has a
  Circumference.
• Is the Area the same as in a polygon?

3
Reminders Continued

• Weve already covered how to find the perimeters
  and areas of simple shapes, but lets go over it
  one last time.
• Squares Rectangles
• Triangles
• Circles

4
Perimeters of More Complicated Shapes

• To find the perimeter of any shape, all you do is
  add of the lengths of all of the sides of that
  shape.
• This works if the shape has three sides, or 1,000
  sides.
• As long as you remember how to add, you can find
  the perimeter of any shape.

5
Areas of More Complicated Shapes

• Area is a little more tricky than perimeter.
• There are many formulas that you can memorize to
  find the areas of different shapes, but thats
  not what this lesson is about.
• Here, we will learn how to find the areas of
  different shapes when we dont have its formula
  memorized.

6
How Can We Find Areas?

• One way of finding the area of a shape is to cut
  it apart.
• All we have to do is cut the shape into pieces
  that we already know how to find the areas of
• Squares, Rectangles, Triangles, and Circles.

7
Houses

• What is the geometric name for a house?
• It has five sides, so its geometric name is a
  pentagon.
• What other shapes can you see in this pentagon?

8
Finding Shapes

• This is the same pentagon from the previous
  slide.
• Its just colored different to make it clear what
  shapes we can cut this pentagon into.

9
Cutting It Apart

• Now, instead of a pentagon, we have a right
  triangle and a square.
• We already know how to find the areas of these
  shapes.

10
Find the Triangle

• To find the area of a triangle, we use the
  formula
• A ½ x Base x Height
• Therefore
• A ½ x 5 in x 12 in
• A 30 in2

11
Find the Area of the Square

• To find the area of a square, we use the formula
• A length x height
• Therefore
• A 13 in x 13 in
• A 69 in2

12
Find the Area of the Pentagon

• Now, add the area of the triangle, to the area of
  the square, and youll have the area of the
  pentagon.
• 30 in2 69 in2 99 in2

13
Practice What Youve Learned

• Thats the end of this lesson, now its time to
  practice what youve learned.
• Heres a worksheet to practice what youve
  learned.
• You may need to use the Pythagorean Theorem on
  this worksheet.
• If you dont remember how that works, check out
  The Pythagorean Puzzle
• Worksheet with Answers