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Warm Up

Warm Up. Problem of the Day. Lesson Presentation. Lesson Quizzes. Warm Up Evaluate. 1 2. 1. · 6 · 8. 24. 1 2. 2. · 5.4 · 7.2. 19.44. 3. 4(7 + 10) ‏. 68. 4. 3.5(12 + 8.2) ‏. 70.7. Problem of the Day. 4 in. 1.5 in. 7 in.

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Warm Up

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  1. Warm Up Problem of the Day Lesson Presentation Lesson Quizzes

  2. Warm Up Evaluate. 1 2 1. · 6 · 8 24 1 2 2. · 5.4 · 7.2 19.44 3. 4(7 + 10)‏ 68 4. 3.5(12 + 8.2)‏ 70.7

  3. Problem of the Day 4 in. 1.5 in. 7 in. An isosceles trapezoid has bases of 7 in. and 4 in. and height 1.5 in. Find its area by using only the formula for the area of a parallelogram. (5.5)(1.5) = 8.25 in2

  4. Learn to find the area of triangles and trapezoids.

  5. Reading Math An altitude of a triangle is a segment that represents the height.

  6. Additional Example 1A: Finding the Area of a Triangle Find the area of the triangle. 1 2 bh A = Use the formula. 5 1 2 Substitute 8 for b and 5 for h. (8 · 5) A = 8 A = 20 The area of the triangle is 20 square units.

  7. Additional Example 1B: Finding the Area of a Triangle Find the area of the triangle. 1 2 Use the formula. A = bh 12 1 2 (9 · 12) A = Substitute 9 for b and 12 for h. 9 A = 54 The area of the triangle is 54 square units.

  8. Check It Out: Example 1A Find the area of the triangle. 1 2 bh A = Use the formula. 1 2 Substitute 6 for b and 9 for h. (6 · 9) A = 9 A = 27 6 The area of the triangle is 27 square units.

  9. Check It Out: Example 1B Find the area of the triangle. 1 2 bh A = Use the formula. 1 2 Substitute 7 for b and 10 for h. 10 (7 · 10) A = A = 35 7 The area of the triangle is 35 square units.

  10. The two parallel sides of a trapezoid are its bases, b1 and b2. The height of a trapezoid is the perpendicular distance between the bases.

  11. Reading Math In the term b1, the number 1 is called a subscript. It is read as “b-one” or “b sub-one.”

  12. Additional Example 2A: Finding the Area of a Trapezoid Find the area of the trapezoid. 1 2 5 in. h(b1 + b2)‏ A = Use the formula. 1 2 · 6(5 + 9)‏ A = Substitute. 6 in. 1 2 Add. · 6(14)‏ A = 9 in. A = 42 Multiply. The area of the trapezoid is 42 in2.

  13. Additional Example 2B: Finding the Area of a Trapezoid Find the area of the trapezoid. 1 2 h(b1 + b2)‏ A = 12 cm Use the formula. 1 2 · 7(12 + 16)‏ A = 7 cm Substitute. 1 2 Add. · 7(28)‏ A = 16 cm A = 98 Multiply. The area of the trapezoid is 98 cm2.

  14. Check It Out: Example 2A Find the area of the trapezoid. 1 2 h(b1 + b2)‏ A = Use the formula. 1 2 · 6(11 + 4)‏ A = Substitute. 11 in. 4 in. 6 in. 1 2 Add. · 6(15)‏ A = A = 45 Multiply. The area of the trapezoid is 45 in2.

  15. Check It Out: Example 2B Find the area of the trapezoid. 1 2 h(b1 + b2)‏ A = Use the formula. 16 cm 1 2 · 9(5 + 16)‏ A = Substitute. 9 cm 1 2 Add. · 9(21)‏ A = 5 cm A = 94.5 Multiply. The area of the trapezoid is 94.5 cm2.

  16. Additional Example 3: Geometry Application The state of Wisconsin is shaped somewhat like a trapezoid. What is the approximate area of the state? 1 2 h(b1 + b2)‏ A = Use the formula. 1 2 · 300(153 + 220)‏ Substitute. A = 1 2 Add. · 300(373)‏ A = A = 55,950 Multiply. The area of Wisconsin is approximately 56,000 square miles.

  17. Check It Out: Example 3 A large preserve has a similar trapezoid shape. What is the approximate area of the preserve? 1 2 232 mi h(b1 + b2)‏ A = Use the formula. 129 mi 1 2 · 129(232 + 116)‏ Substitute. A = 116 mi 1 2 Add. · 129(347)‏ A = A = 22,446 Multiply. The area of the preserve is approximately 22,000 square miles.

  18. Lesson Quizzes Standard Lesson Quiz Lesson Quiz for Student Response Systems

  19. Lesson Quiz Find the area of each figure. 1. 3. 9 in2 2. 45 ft2 4. 60 ft2 87.5 ft2 4. What is the height of a triangle with area 36 cm2 and a base 9 cm? 8 cm

  20. Lesson Quiz for Student Response Systems • 1. Identify the area of the triangle. • A. 35 in2 • B. 70 in2 • C. 105 in2 • D. 140 in2

  21. Lesson Quiz for Student Response Systems • 2. Identify the area of the triangle. • A. 264 m2 • B. 132 m2 • C. 66 m2 • D. 46 m2

  22. Lesson Quiz for Student Response Systems • 3. Identify the area of the trapezoid. • A. 117 in2 • B. 162.5 in2 • C. 255 in2 • D. 279.5 in2

  23. Lesson Quiz for Student Response Systems • 4. What is the base of a triangle with area 66 m2 and height 11 m? • A. 6 m • B. 8 m • C. 10 m • D. 12 m

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