7.RP.2 & 7.G.1

I can ~ compare, create, and match corresponding figures in

scale drawings.I can ~ find the unit rate as the

scale factor.

Can you guess the image?

Was the second photo a reduction or an enlargement of the original picture?

How do you know?

How about this image?

Was the second photo a reduction or an enlargement of the original picture?

How do you know?

Scale drawing: A reduced or enlarged two-dimensional drawing of an original

two-dimensional drawing.

R W P N

* Why doesn’t point V correspond to point R?

* What must we consider before we identify corresponding points?

Exploratory Challenge: Make your own scale drawing.

*Notice the grids are either enlarged or reduced in size.

*You are to create a scale drawing on each of the grids.

*Will you need to adjust the number of units on each part of the robot?

*What is the importance of matching corresponding points?

*How can you check the accuracy of your scale drawing?

Do your scale drawings look like this?

*Now look at the second set of drawings.*Fill in the table to the right.*What do you notice about the information in the table?*Does a constant of proportionality exist? How do you know?*What is the constant of proportionality?*If there was no constant, would the drawings be proportional?

18 6

9 3

Now work on the next set of drawings on your

own…

•Does a constant of proportionality exist?

•Is Luca’s enlarged mosaic a scale drawing of the first image?

•Why or why not?

Steps to check proportionality:

• Measure the lengths of the scale figure.

• Measure the corresponding lengths of the actual figure.

• Check for a constant of proportionality.

Are the cubes proportional?

What about the app icon?

Notes:Scale drawing: A drawing in which all lengths

between points or figures in a drawing are proportional to the actual picture.

Reduction: The lengths in the scale drawing are smaller than the actual drawing.

Enlargement: The lengths in the scale drawing are larger than the actual drawing.

One-to-one Correspondence: Each point in one figure corresponds to one and only one point in the second figure.

Now, let’s practice with scale factor!

Practice check

Questions?

Exit Ticket:Hayden likes building radio-controlled sailboats with her father. One of the sails, shaped like a right triangle, has side lengths measure 6 inches, 8 inches, and 10 inches. To log her activity, Hayden creates and collects drawings of all the boats she and her father built together. Using the scale factor of ½ , write the dimensions of the reduced sail.