Unit 4a – Geometry Two Dimensional Figures –
Class Notes
Date
Perimeter
Learning Target: I can calculate perimeter of polygons.
Key Terms

Perimeter: The distance around a polygon.
Examples
Example A: Finding the Perimeter of a Polygon
Example B: Using a Formula to Find Perimeter
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Example C: Finding Unknown Side Lengths
Try This
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Date
Area of Rectangles and Parallelograms
Learning Target: I can calculate the area of rectangles and parallelograms.
Key Terms

Area: The number of square unit needed to cover a given surface.
Examples
Area of Rectangles and Parallelograms
Try This
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Page 3
Date
Area of Trapezoids and Triangles
Learning Target: I can calculate the area of trapezoids and triangles.
Example:
Try This:
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Page 4
Date
Area of Compound Figures
Learning Target: I can calculate the area of compound figures.
Important Information
You know how to find the area of rectangles, parallelograms, triangles and trapezoids. To find the area
of compound figures, break them into simpler polygons first. Once you find their areas, simply add
them all together.
Example
Try This
1)
2)
3)
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4)
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Date
Area Real-World Problems
Learning Target: I can solve real-world problems involving area.
Try This:
1) Roberto has four 4 ft. by 6 ft. carpet remnants that he will use to cover a game room floor. If
the floor is 9 ft. by 12 ft., does he have enough carpet to cover the floor? Explain.
2) What is the height of a parallelogram with an area of 66 in² and a base of 11 in?
3) A dollar bill is 15.5 cm long and 6.5 cm. wide. What is the area of a dollar bill?
4) A local grocery store has diagonal parking spaces that are shaped like parallelograms. If a space
is 9 ft. wide and 24 ft. long, what is the area?
5) When the Erie Canal opened, it was 42 feet wide at the top, 28 feet wide at the bottom, and 4
feet deep. Find the area.
6) What is the height of a trapezoid with an area of 9m² and bases that measure 2.4 m and 3.6 m?
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7) A triangular road sign has a height of 8 feet and a base of 16.5 feet. How much larger in area is
this sign than one with a height of 4 feet and a base of 8.25 feet?
8) What is the height of a triangle with area 36 cm² and base 9 cm?
9) Gina used tiles to create a design. The lengths of all the sides are 3 cm, except for two larger
sides that are 9cm. What is the area of Gina’s design?
10) Edgar plants daffodils around a rectangular pond. The yellow part of
the diagram shows where the daffodils are planted. What is the
area of the yellow part of the diagram?
11) Sam made a wall hanging. All the sides are 6 inches long, except for two longer sides that are
each 12 inches. All the angles are right angles. What is the area of the wall hanging?
12) The perimeter of this figure is 42.5 cm. Find the area of the
figure.
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Page 7
Date
Area in the Coordinate Plane
Learning Target: I can calculate the area within the coordinate plane.
Steps:
1. Graph the given coordinates on the coordinate plane.
2. Determine the needed measurements. Ex. length, width, base or height.
3. Using the appropriate formula; find the area.
Example:
Graph the polygon with the given vertices and then find the area.
(1, 2), (4, 5), (8, 2), (8,5)
Step 1: Plot points on grid.
Step 2: Base 1 = 7 units
Base 2 = 4 units
Height = 3 units
Step 3: Area of trapezoid
A = ½ h (b₁ + b₂)
A = ½ (3) (7 + 4)
A = 1.5(11)
A = 16.5 units ²
Try This
Graph the polygon with the given vertices and then find the area.
1) (1, 2), (3, 5), (7, 2), (9,5)
2) (4, 1), (4, 7), (8,4), (8, 10)
3) (2, 3), (2, 10), (7,6), (7,8)
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4) (3, 0), (3, 4), (-3, 0)
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