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MJ3

MJ3 . Ch 7.1 – Area of Parallelograms, Triangles & Trapezoids. Bellwork. Get your bellwork sheet and a pencil and meet me in front of the media center. After The Activity. Raise you hand if you can predict why I had you do this activity… What is perimeter? What is Area?

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MJ3

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  1. MJ3 Ch 7.1 – Area of Parallelograms, Triangles & Trapezoids

  2. Bellwork • Get your bellwork sheet and a pencil and meet me in front of the media center.

  3. After The Activity • Raise you hand if you can predict why I had you do this activity… • What is perimeter? • What is Area? • From a rectangle we can create a parallelogram…(demonstrate w/index card) • My comments….

  4. Assignment Review • None

  5. Before we begin… • Please take out your notebook and get ready to work… • In the bellwork activity we looked at the perimeter of a square… • At this stage you should all know the difference between perimeter and area… • More specifically, you should know by rote memory how to calculate the area of a square or rectangle… • In today’s lesson we will look at how to calculate the area of parallelograms, triangles and trapezoids…

  6. Objective 7.1 • Students will calculate the area of parallelograms, triangles and trapezoids using the formula method

  7. The Formula Method • First and foremost…in this chapter the only way that I will accept any answers is if you use the formula method! • At this level you are required to demonstrate what you know and the formula method helps you do that. • The formula method is: • Write the formula • Substitute • Do the math Note: Each time you perform a function you must rewrite the whole equation all over again…this strategy minimizes errors!

  8. Example • Calculate Area: A = l ● w 1. Write the Formula A = 4 ● 8 2. Substitute A = 32 ft2 3. Do the math Note: The answer is squared because you are measuring 2 dimensions (Length & Width) 4 ft 8 ft

  9. Parallograms • Let’s look at the specific characteristics of a parallelogram… • In a parallelogram the base can be any side. • The height (altitude) is a line segment that is perpendicular to the base and runs to the opposite side. • The formula for area of a parallelogram is: A = bh • The formula can be found on the FCAT reference sheet

  10. Example • Find Area 1. Write the Formula A = bh 12 m 2. Substitute A = 5.25(12) 3. Do the math A = 63 m2 5.25 m

  11. Your Turn • In the notes section of your notebook draw and label the picture and then calculate area using the formula method. 25 mm 16.25 ft 5 mm 8 ft

  12. Triangles • A diagonal drawn in a Parallograms will separate the parallelogram into 2 congruent triangles • Therefore, the area of a triangle will be ½ of the area of a parallelogram • The base can be any side and the height (altitude) is the line segment from the base to the opposite side. • The formula for area of a triangle is A = ½ bh • You can find this formula on the FCAT reference sheet Height Base

  13. Example • Calculate Area 4.5 m 8.5 m 1. Write the Formula A = ½ bh 2. Substitute A = ½ (8.5)(4.5) 3. Do the math A = ½ (38.25) A = 19.125 m2

  14. Your Turn • In the notes section of your notebook draw and label the figure and then calculate area using the formula method 10 m 18 m 6 ft 20 m 12 m 10.5 ft

  15. Parallel Sides Trapezoids • In chapter 6 we discussed trapezoids, which are quadrilaterals with 2 parallel sides. • The parallel sides are the bases. It doesn’t matter which one you call b1 or b2 • The formula for area of trapezoids is A = ½ h(b1 + b2) • This formula can also be found on the FCAT reference sheet

  16. Example 9 mm • Calculate Area 4.5 mm 6.5 mm 18.5 mm 1. Write the Formula A = ½ h(b1 + b2) 2. Substitute A = ½ (6.5)(18.5 + 9) 3. Do the math A = ½ (6.5)(27.5) A = ½ (178.75) A = 89.375 mm2

  17. Your Turn • In the notes section of your notebook draw and label the figure and then calculate area using the formula method. 9 cm 3.2 cm 6.5 cm 4 cm

  18. Summary • In the notes section of your notebook summarize the key concepts covered in today’s lesson • Today we discussed • The difference between perimeter & area • How to calculate area using the formula method

  19. Assignment • Text p. 317 # 7 – 15 • You do not have to draw the figure. • However, you must use the formula method to show how you got your answer. (no work = no credit) • This assignment is due tomorrow • I do not accept late assignments

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