# Illustrative Mathematics Grade 7, Unit 3, Lesson 11: Stained-Glass Windows

Learning Targets:

• I can apply my understanding of area and circumference of circles to solve more complicated problems.

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Illustrative Math

#### Lesson 11: Stained-Glass Windows

Let’s use circumference and area to design stained glass windows.

Illustrative Math Unit 7.3, Lesson 11 (printable worksheets)

#### Lesson 11.1 Cost of a Stained-Glass Window

The students in art class are designing a stained-glass window to hang in the school entryway. The window will be 3 feet tall and 4 feet wide. Here is their design.
They have raised \$100 for the project. The colored glass costs \$5 per square foot and the clear glass costs \$2 per square foot. The material they need to join the pieces of glass together costs 10 cents per foot and the frame around the window costs \$4 per foot.
Do they have enough money to cover the cost of making the window?

#### Lesson 11.2 A Bigger Window

A local community member sees the school’s stained glass window and really likes the design. They ask the students to create a larger copy of the window using a scale factor of 3. Would \$450 be enough to buy the materials for the larger window? Explain or show your reasoning.

#### Lesson 11.3 Invent Your Own Design

Draw a stained glass window design that could be made for less than \$450. Show your thinking. Organize your work so it can be followed by others.

The Open Up Resources math curriculum is free to download from the Open Up Resources website and is also available from Illustrative Mathematics.

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