8.1 - Similar Shapes 1

8.1 - Similar Shapes

LO: SWBAT identify the similar shapes

CCLS: 7.G.1

Open Ended

OPENING ASSESSMENT: Write down the numbers of the two diagrams that show similar shoes. Explain how you know.

scale factor -  is the ratio between corresponding measurements of an object and a representation of that object

Practice Problem Time!

Use your notes to help you solve these practice problems. Be ready to share how you found your answer!

Multiple Choice

Similar figures always have _____.

• the same shape and same size

• the same shape, but can be different sizes

• the same size, but can be different shapes

Multiple Choice

The corresponding angles of similar figures are _______.

• congruent

• proportional

• not the same

Multiple Choice

The corresponding sides of similar figures are _______.

• the same

• proportional

• not the dame

Multiple Choice

The triangles below are similar.  What is the scale factor of triangle ABC to triangle DEF?

• 2

• 3

•  $\frac{1}{4}$ 

• $\frac{1}{2}$

EXPLANATION

The second triangle listed is 3 times as large. If you use the ratios, 27/9 = 3 and 21/7 = 3. The second triangle listed is larger, so the scale factor is larger than 1.

Multiple Choice

The triangles below are similar.  What is the scale factor of triangle DEF to triangle ABC?

• 2

• 3

•  $\frac{1}{3}$ 

• $\frac{1}{2}$

EXPLANATION

This time, the second triangle listed is smaller so the scale factor is smaller than 1. You can use the reciprocal of the answer you got from the previous problem or use the ratios. Make sure to put the smaller number on top if you find the ratios: 9/27 and 7/21 both reduce to 1/3.

Multiple Choice

The scale factor of triangle ABC to triangle DEF is 6. Which description is correct?

• Triangle ABC is 6 times larger than triangle DEF

• Triangle DEF is 6 times larger than triangle ABC.

Poll

How well do you feel you understand this material?

• Totally got it! I'm ready to work on my assignment.

• Mostly get it, but I'd like to see another example before starting my assignment.

• Kind of get it, but I have a couple questions/need a few more examples before I start working.

• I don't understand this at all. Please help! I need more examples/explanation.