9-2 Area of Triangles and Trapezoids Warm Up Warm Up Lesson Presentation Lesson Presentation Problem of the Day Problem of the Day Lesson Quizzes Lesson Quizzes

9-2 Area of Triangles and Trapezoids Warm Up 1. True or false: If the height of a rectangle equals the base of a parallelogram and the base of the rectangle equals the height of the parallelogram, then the rectangle and the parallelogram have the same area. 2. Find the area of a rectangle with a length of 53 in. and a width of 47 in. True 2,491 in 2

9-2 Area of Triangles and Trapezoids Problem of the Day 3/$5.00 Which is a better deal, 3 discs for $5.00 or 4 discs for $7.00?

9-2 Area of Triangles and Trapezoids You can divide any parallelogram into two congruent triangles. So the area of each triangle is half the area of the parallelogram.

9-2 Area of Triangles and Trapezoids

9-2 Area of Triangles and Trapezoids Find the area of the triangle. Additional Example 1: Finding the Area of a Triangle A = 1212 bh Write the formula. A = 1212 (20 · 12) Substitute 20 for b and 12 for h. A = 120 The area is 120 ft 2. A = 1212 (240) Multiply.

9-2 Area of Triangles and Trapezoids An altitude of a triangle is a perpendicular segment from one vertex to the line containing the opposite side. The length of the altitude is the height. Reading Math

9-2 Area of Triangles and Trapezoids Check It Out: Example 1A Find the area of the triangle. 11 cm 4 cm A = bh = (11 4) = 22 cm __ 1 2 2

9-2 Area of Triangles and Trapezoids The diagram shows the floor plan for a triangular dining area. What is the area of the floor? Check It Out: Example 1B 6.2 m A = 1212 bh = 1212 ( ) = m 34.8 m

9-2 Area of Triangles and Trapezoids The diagram shows the section of a forest being studied. What is the area of the section? Additional Example 2: Application A = 1212 bh Write the formula. A = 1212 ( ) Substitute 43.9 for b. Substitute 16 for h. A = The area is km 2. A = 1212 (702.4) Multiply.

9-2 Area of Triangles and Trapezoids Check It Out: Example 2A Mitch uses the piece of wood shown as part of a skateboard ramp. Its area is 0.8 m. What is the height of the piece of wood?. A = bh; 0.8 = (2) 0.8 = h The height is 0.8 m. h 1 2 __ m 2

9-2 Area of Triangles and Trapezoids Check It Out: Example 2B Mitch wants his skateboard ramp to be at least 750 cm tall. Should he use this piece of wood to build the ramp? Explain.?. Yes; the height is 0.8 m or 800 cm, which is greater than 750 cm.

9-2 Area of Triangles and Trapezoids

9-2 Area of Triangles and Trapezoids Find the area of the trapezoid. Additional Example 3: Finding the Area of a Trapezoid A = 1212 h(b 1 + b 2 ) ‏ Use the formula. A = 53 The area is 53 yd 2. Multiply. A = 1212 · 4(26 ) ‏ 1 2 Substitute 4 for h, 14 for b 1, and 12 for b A = 1212 · 4( ) ‏ 1 2

9-2 Area of Triangles and Trapezoids Check It Out: Example 3A Lisa wants to cut a hole in the shape of a trapezoid out of a piece of wood. The figure shows her plans, and each square of the grid represents 1 ft. What is the area of the remaining wood after she cuts out the hole? 2

9-2 Area of Triangles and Trapezoids Check It Out: Example 3A continued 5 × 8 = 40; The remaining area is 26.5 ft = 26.5 (3 + 6)3 = 13.5; 1 2 _

9-2 Area of Triangles and Trapezoids Check It Out: Example 3B The figure shows a vegetable garden that is planted with squash and carrots. To the nearest percent, how much of the vegetable garden is for squash?

9-2 Area of Triangles and Trapezoids Check It Out: Example 3B continued About 43% of the vegetable garden is for squash. (8 + 6)3 = 21; (6)(3) = 9; =, or about _ 3 7 _ 1 _ 2 1 _ 2

9-2 Area of Triangles and Trapezoids Standard Lesson Quiz Lesson Quizzes Lesson Quiz for Student Response Systems

9-2 Area of Triangles and Trapezoids Lesson Quiz Find the area of each triangle mi cm m in Find the area of each trapezoid.

9-2 Area of Triangles and Trapezoids 1. Find the area of the triangle. A cm 2 B cm 2 C cm 2 D cm 2 Lesson Quiz for Student Response Systems

9-2 Area of Triangles and Trapezoids 2. Find the area of the triangle. A. 124 m 2 B. 134 m 2 C. 132 m 2 D. 144 m 2 Lesson Quiz for Student Response Systems

9-2 Area of Triangles and Trapezoids 3. Find the area of the trapezoid. A m 2 B m 2 C m 2 D m 2 Lesson Quiz for Student Response Systems