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Warm Up Find the area of each figure. Give exact answers, using  if necessary.

Warm Up Find the area of each figure. Give exact answers, using  if necessary. 1. a square in which s = 4 m 2. a circle in which r = 2 ft 3. What’s bigger: two 10in pizzas or a 20in pizza? Are they the same? . 16 m 2. 4 ft 2. Lesson 9-5 Effects of Changing Dimensions.

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Warm Up Find the area of each figure. Give exact answers, using  if necessary.

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  1. Warm Up Find the area of each figure. Give exact answers, using  if necessary. 1.a square in which s = 4 m 2. a circle in which r = 2 ft 3. What’s bigger: two 10in pizzas or a 20in pizza? Are they the same? 16 m2 4 ft2

  2. Lesson 9-5 Effects of Changing Dimensions

  3. Find the perimeter and area of each rectangle. Compare the larger rectangle to the smaller using division. Rectangle A Rectangle B 2” 4” 3” 6” P = P = A = A =

  4. What if we only change length and leave width alone? Rectangle A: 2x4 Rectangle B: 6X4 What was the scale factor for the length change? How did this affect the Area?

  5. What if we change length and width but by different factors? Rectangle A:2x4 Rectangle B:6x8 Length change factor: Width change factor: Area change:

  6. Is this true for all shapes or just rectangles? Consider circles Circle A: r = 3 Circle B: r = 9 Scale Factor for radius? Area change?

  7. What about Squares? Square A: s=4 Square B: s = 12 Scale factor? Area change?

  8. When the dimensions of a figure are changed proportionally, the figure will be similar to the original figure.

  9. Helpful Hint Helpful Hint Example 3A: Effects of Changing Area A circle has a circumference of 32 in. If the area is multiplied by 4, what happens to the radius? Helpful Hint

  10. An equilateral triangle has a perimeter of 21m. If the area is multiplied by , what happens to the side length? Example 3B: Effects of Changing Area

  11. Summary The relationship between perimeter and area of similar figures is as follows: • If you know the change in perimeter, the area is changed by that number squared. • If you know the change in area you can square root to find the change in perimeter. Homework: p625 1-7,30-32,41,42 Quiz tomorrow! Test on Thursday!

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