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

2. 3/2 News and Notes Perfection Award: 4 th 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. 3 6 9 16 8 x 43° A BC D E F

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 16 8 24 D E F 4 2 x G HI

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-imageImage 3 2 8 X 15 24 8 10 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