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3/2 Bell Ringer

3/2 Bell Ringer. Homework: Finish scale factor guided notes and independent practice. DE//BC. If AD = 3, DB = 4, and DE = 5, set up a proportion to solve for BC. . Grab a calculator and today’s packet!. 3/2 News and Notes. Perfection Award : 4 th PERIOD

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3/2 Bell Ringer

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  1. 3/2 Bell Ringer Homework: Finish scale factor guided notes and independent practice DE//BC. If AD = 3, DB = 4, and DE = 5, set up a proportion to solve for BC. Grab a calculator and today’s packet!

  2. 3/2 News and Notes • Perfection Award: 4th PERIOD • Remember, Unit 7 Hawkeye on Similarity will be next Tuesday. START GETTING READY!!!! • Hand in yesterday’s 2-page packet.

  3. 3/2 Agenda • I CAN apply knowledge of scale factor to similar figures. • 1. Bell Ringer • 2. Intro to New Material • 3. Guided Practice • 4. Independent Practice • 5. ACT Question of the Day

  4. What is a scale factor? • The scale factor is the answer to the question: By how much did my pre-image get bigger or smaller? • Therefore, to find the scale factor, do these two things: • 1. Identify corresponding parts (pre-image and image). • 2. Scale factor =

  5. Reduction or Enlargement? • Your pre-image will get smaller IF the scale factor is between 0 and 1. • Your pre-image will get bigger IF the scale factor is greater than 1. • Your pre-image rotates if the scale factor is less than 0. (Size follows above rules).

  6. Intro to New Material – Example 1 • ∆ABC ~ ∆DEF. Assume ABC is the pre-image. Find scale factor, then find x. • Scale factor = = DE/AB = 8/3 = 2.666. • X = 9(2.666666) = 24. D A 9 x 43° 3 8 B C 6 E F 16

  7. Example • What if ∆DEF is the pre-image and we are shrinking? • Scale factor = = GH/DE = 2/8 = ????? • ¼!!! • X = 24(1/4) = 6 D G 24 x 8 2 H I 4 E F 16

  8. Guided Practice • Think- Pair-Share • Step 1: You pick 1 problem to start and your partner gets the other. • Step 2: Find the scale factor. STOP AND WAIT • Step 3: Trade papers. • Step 4: Check partner’s work, then use scale factor to find x. STOP AND WAIT • Step 5: Talk with partner about answer. • Step 6: Check your answers with group behind or in front of you.

  9. #1 #2 Pre-image Pre-image Image Image 24 15 3 2 8 10 X 8 X

  10. Independent Practice • You now have the rest of class to work on the independent practice problems. • We will finish with the ACT Question of the Day in the last 3 minutes of class.

  11. ACT Question of the Day • A rectangle with dimensions 6x9 undergoes a dilation by a scale factor of 3. What are the dimensions of the image rectangle and did it get bigger or smaller? • A. 2x3; Reduction • B. 18x27; Reduciton • C. 18x27; Enlargement • D. 2x3; Enlargement Homework: Finish scale factor guided notes and independent practice

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