Geometry Formal Geometry Lesson 9 Area of Quadrilaterals ... · Area of Quadrilaterals Reteach You can use formulas to find the areas of quadrilaterals. The area A of a parallelogram

Name ________________________________________ Date __________________ Geometry/Formal GeometryLesson 9

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262

Area of Quadrilaterals Reteach

You can use formulas to find the areas of quadrilaterals.

The area A of a parallelogram is the product of its base b and its height h.

A = bh

A = bh = 3 • 7 = 21 cm2

The area of a trapezoid is half its height multiplied by the sum of the lengths of its two bases.

A = 12 h(b1 + b2)

A = 12 h(b1 + b2)

= 12 • 6(5 + 9)

= 12 • 6(14)

= 3 • 14 = 42 m2

The area of a rhombus is half of the product of its two diagonals.

A = 12

d1d2

A = 12 d1d2

= 12

(5)(8)

= 20 in2

Find the area of each figure. 1. 2.

________________________________________ ________________________________________

3. 4.

________________________________________ ________________________________________

LESSON

13-1

Name ________________________________________ Date __________________ Geometry/Formal


268

Area of Triangles Reteach

To find the area of a triangle, first turn your triangle into a rectangle.

Next, find the area of the rectangle. 6 • 3 = 18 square units

The triangle is half the area of the formed rectangle or A = 12 bh, so

divide the product by 2.

18 ÷ 2 = 9 So, the area of the triangle is 9 square units.

Find the area of each triangle. 1. 2.

________________________________________ ________________________________________

3. 4.

________________________________________ ________________________________________

5. 6.

________________________________________ ________________________________________

LESSON

13-2



259

Area of Quadrilaterals Practice and Problem Solving: A/B

Find the area of each parallelogram. 1. 2.

________________________________________ ________________________________________

Find the area of each trapezoid. 3. 4.

________________________________________ ________________________________________

Find the area of each rhombus. 5. 6.

________________________________________ ________________________________________

Solve. 7. A desktop in the shape of a parallelogram has a base of 30 inches and

a height of 40 inches. What is the area of the desktop?

___________________________

8. A rhombus has one diagonal that is 14 centimeters long and onediagonal that is 12 centimeters long. What is the area of the rhombus?

___________________________

9. The bases of a trapezoid are 24 feet and 16 feet. The height of thetrapezoid is 12 feet. What is the area of the trapezoid?

___________________________

LESSON

13-1



265

Area of Triangles Practice and Problem Solving: A/B

Find the area of each triangle. 1. 2.

________________________________________ ________________________________________

3. 4.

________________________________________ ________________________________________

Solve. 5. The front part of a tent is 8 feet long and 5 feet tall.

What is the area of the front part of the tent?

___________________________

6. Kathy is playing a board game. The game pieces areeach in the shape of a triangle. Each triangle has abase of 1.5 inches and a height of 2 inches. What isthe area of a game piece?

___________________________

7. A triangular-shaped window has a base of 3 feet and a heightof 4 feet. What is the area of the window?

___________________________

8. Landon has a triangular piece of paper. The base of the paper

is 6 12

inches. The height of the paper is 8 inches. What is the

area of the piece of paper?

___________________________

LESSON

13-2

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Geometry Formal Geometry Lesson 9 Area of Quadrilaterals ... · Area of Quadrilaterals Reteach You can use formulas to find the areas of quadrilaterals. The area A of a parallelogram

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