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# Area of triangles - PowerPoint PPT Presentation

Area of triangles. Unit 5. Getting the idea. Area is a measure of the number of square units needed to cover a region. Square Unit is a square with a side length of 1 of any particular unit of measure. Square Inches = in 2 Square Centimeters = cm 2. Formula for area of a triangle.

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### Area of triangles

Unit 5

• Area is a measure of the number of square units needed to cover a region.

• Square Unit is a square with a side length of 1 of any particular unit of measure.

• Square Inches = in2

• Square Centimeters = cm2

• Area equals one-half the base (b) times the

height (h).

• A = ½bh

h

b

h

b

• Step One: Determine the formula for the area of a triangle.

• A = ½ bh

• Step Two:Substitute the values for the baseand the height

into the formula.

• The base, b, measures 8 inches and the height, h, measures

4 inches.

• A = ½ (8)(4)

• Step Three: Multiply

• A = ½ (8)(4)

• A = ½ (32) = ● =

• A = *divide by 2*

• A = 16

• Step Four: Write the answer with correct unit of measure squared.

• Area = 16 in2

• 4 in

8 in

• Remember that a right triangle has a hypotenuse and 2 sides called legs.

• The legs form a right angle.

• To find the area of a right triangle, use the legs as the base and height.

Hypotenuse

• Step One: Determine the formula for the area of a triangle.

• A = ½ bh

• Step Two:Substitute the values for the base and the heightinto the formula.

• The base, b, measures 9 cm and the height, h, measures 3 cm.

• A = ½ (9)(3)

• Step Three: Multiply

• A = ½(9)(3)

• A = ½ (27) = ● =

• A = *divide by 2*

• A = 13.5

• Step Four: Write the answer with correct unit of measure

squared.

• Area = 13.5 cm2

• 3 cm

9 cm

• In an obtuse triangle, you can extend a side to find the height.

Obtuse Angle: Angle greater than 90˚

• Step One: Determine the formula for the area of a

triangle.

• A = ½ bh

• Step Two:Substitute the values for the base and the height

into the formula.

• The base, b, measures 12 feet and the height, h, measures 5 feet.

• A = ½ (12)(5)

• Step Three: Multiply

• A = ½(12)(5)

• A = ½ (60) = ● =

• A = *divide by 2*

• A = 30

• Step Four: Write the answer with correct unit of measure squared.

• Area = 30 ft2

• 5 ft

12 ft

4. What is the height of a triangle with an area of 40m2and a base of 10 m?

• Step One:Determine the formula for the area of a triangle.

• A = ½ bh

• Step Two:Substitute the values for the areaand the base into the formula.

• The Area , A, is 40 m2 and the base, b, measures 10 m.

• 40 = ½ (10)(h)

• Step Three: Solve the Equation

• 40 = ½ (10)(h) = ● (h) = (h) = 5h

• 40 = 5h *divide both sides of equal sign by 5 (isolate the variable)

• 8= h

• Step Four: Write the answer with correct unit of measure.

• height = 8 m

• 5. The Clarke family built a triangular deck at the back of their house. What Is the area of the triangular deck if the base is 9 yards and the height is 7 yards?

• Draw the triangular deck and label the base and the height.

• Write the formula for finding the area of a triangle.

• Substitute the base and height into the formula.

• Solve the formula to determine the area of the triangular deck.

6. A triangular pennant has a base that is 18 inches long and a height of 6 ½ inches. What is the area of the pennant?

• Draw the triangular pennant and label the base and the height.

• Write the formula for finding the area of a triangle.

• Substitute the base and height into the formula.

• Solve the formula to determine the area of the triangular pennant.

7. The Area of a triangle is 30 yd2 and its height is 6 yd. What is the length of the base?

• Write the formula for finding the area of a triangle.

• Substitute the Area and height into the formula.

• Solve the formula to determine the base of the triangle.

34 in

34 in

• 1. What is the area of Triangle A?

• 2. What is the area of Triangle B?

• 3. Describe what you notice about the two triangles.

18 in

26 in

30 in

30 in

Triangle A

26 in

Triangle B