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Finding Area and Perimeter of Polygons

Finding Area and Perimeter of Polygons. Area. Definition : The number of square units needed to cover a surface. (INSIDE) Length x width. Perimeter. Definition: The sum of the length of all the sides of a polygon. Base. Definition: A side or face of a figure on which the figure stands.

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Finding Area and Perimeter of Polygons

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  1. Finding Area and Perimeter of Polygons

  2. Area • Definition: • The number of square units needed to cover a surface. (INSIDE) • Length x width

  3. Perimeter • Definition: The sum of the length of all the sides of a polygon.

  4. Base • Definition: • A side or face of a figure on which the figure stands.

  5. Height • Definition: • The distance from the bottom to the top of a figure.

  6. Width • Definition: • How wide a figure is from side to side.

  7. Length • Definition: • The measure of the distance across an figure.

  8. How to findArea.

  9. Finding area of an irregular figure • Box the object in then count the length and the width of the “box”. • Example: • Length = 4 • Width = 5

  10. Finding area of an irregular figure Hint: Length x width=area What is the area of the box?

  11. Finding area of an irregular figure Hint: Length x width=area What is the area of the box? Right! 4x5=20

  12. Finding area of an irregular figure • How many squares are there in the box that are not shaded?

  13. Finding area of an irregular figure • How many squares are there in the box that are not shaded. • Right! • 6 squares

  14. Finding area of an irregular figure The area of the object is the area of the “box” (20) minus the squares that are are not shaded (6).

  15. Finding area of an irregular figure The area of the object is 20-6= 14 The area of the irregular figure is 14. *This method can be used instead of counting all the squares.

  16. How to findperimeter.

  17. Finding perimeter of a figure • Perimeter: distance around an object. • In this case the Box.

  18. Finding perimeter of a figure • For this figure the length is 4 and the width is 5. You have two 4’s and two 5’s. • The perimeter is • 2x4 + 2x5 = perimeter

  19. Finding perimeter of a figure • Multiply first, then add: • The perimeter is • 2x4 + 2x5 = perimeter • 8 + 10 =

  20. Finding perimeter of a figure • Multiply first, then add: • The perimeter is • 2x4 + 2x5 = perimeter • 8 + 10 = 18 • The perimeter of the box is 18.

  21. Finding perimeter of a figure 18 is the perimeter of the box. So what? We want to know the perimeter of the figure.Do we know the perimeter of the figure?

  22. Finding perimeter of a figure • Yes, the perimeters are the same. • The blue is the perimeter of the figure. • The red is the perimeter of the box.

  23. Finding perimeter of a figure That trick does not work all the time. Sometimes you may have to count the side and add. What is the perimeter of this figure?

  24. Finding perimeter of a figure What is the perimeter of this figure?

  25. Finding perimeter of a figure Right 20! 10 on top and bottom 10 on the right and left

  26. Now Go to: www.shodor.org/interactivate/activities/perimeter/

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