Transparency 2 Click the mouse button or press the Space Bar to display the answers.

Example 2-1a Objective Find the areas of triangles

Example 2-1a Vocabulary Triangle A polygon with 3 sides

Lesson 2 Contents Example 1Find the Area of a Triangle Example 2Find the Area of a Triangle Example 3Use Area to Solve a Problem

Example 2-1a Find the area of the triangle. Write formula for area of a triangle Count number of units of the length of a base Base Replace b with 5 units  5 units 1/2

Example 2-1a Find the area of the triangle. Count number of units of the height Height Replace h with 8 units  5 units  8 units /2

Example 2-1a Find the area of the triangle.  5 units  8 units 1/2 Multiply the numbers  5  8 A = 20 Multiply the units unit  unit unit 2 Answer:

Example 2-1b Answer: 9 units 2 Find the area of the triangle. 1/2

Example 2-2a Find the area of the triangle. Round to the nearest hundredth 2/2 Write formula for area of a triangle Replace b with 16.4 cm  16.4 cm Replace h with 7.9 cm  7.9 cm Remember: The base is opposite the vertex

Example 2-2a Find the area of the triangle. Round to the nearest hundredth 2/2  16.4 cm  7.9 cm Multiply the numbers  16.4  7.9 A = Multiply the units cm  cm cm 2 Answer: Since the dimensions are decimals the answer must be decimals

Example 2-2b Find the area of the triangle. Round to the nearest hundredth Answer: in 2 2/2

End of Lesson 2 Assignment Lesson 14:2Area of Triangles All

Example 2-3a MULTIPLE-CHOICE TEST ITEM Which ratio compares the area of the shaded triangle to the area of the large square? A 1 to 2B 1 to 4C 1 to 8D 1 to 16 3/3

Example 2-3a Read the Test Item You need to find the ratio that compares the area of the shaded triangle to the area of the large square. Solve the Test Item First find the area of the triangle and the area of the square. Area of Triangle Area of Square 3/3

Example 2-3a Answer: C Since, the ratio is 2 to 16, or 1 to 8 in simplest form. Now find the ratio. 3/3

Example 2-3b Answer: B MULTIPLE-CHOICE TEST ITEM Which ratio compares the area of the shaded triangle to the area of the large square? A 1 to 2B 1 to 4C 1 to 8D 1 to 16