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# Applying the Area Formulas for Regular Polygons

Lesson 2 of 11

## Objective: SWBAT apply the area formulas for regular polygons.

*45 minutes*

#### Do Now

*10 min*

In the previous lesson, Developing Area Formulas, students developed area formulas for regular polygons. The Do Now focuses on the area of a rectangle, but students need to think logically about the problem.

**Do Now**

**A rectangle measures 3 in by 4 in. If the lengths of each side double, what is the effect on the area?**

Students may initially think that the area doubles because each side length doubles. I will suggest to students that they actually calculate the area of both rectangles, to determine the affect on the area. Once students have done this, they will realize that the area quadruples.

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#### Independent Practice

*15 min*

For the Independent Practice students will use the area formulas to help them complete the Finding the Finding the Area of Regular Polygons Worksheet. Although students should work independently, they may want to discuss or ask questions of their group.

Students will have 15 minutes to complete the worksheet.

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#### Group Work

*15 min*

Students are heterogeneously grouped. I will assign each group a problem from the Finding the Area of Regular Polygons Worksheet. Students should discuss their work and answers with their group. When they are in agreement, I will give groups chart paper and colored pencils for them to show their work. Students will have 10 minutes to complete their work.

After 10 minutes, the group work will be posted around the classroom for a roundtable activity. For this activity, students should have the worksheet and their work with them. Students will rotate to each group work. At each problem, students will review the completed work and compare it to their work. Post it notes will be available for students to write comments or ask questions. After the groups have rotated to each problem, they should end back up at their chart paper. I will give the groups time to reflect on any comments or questions they may have received. If there is any confusion, we will discuss it at this time.

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#### Exit Ticket

*5 min*

At the end of this lesson students will be given an area problem to solve. The results of this exit ticket will be used for future grouping.

The challenge of this problem is that the area and base is given, but students have to work backwards to find the height. Also, the base is given as a decimal, so students may have difficult finding 1/2 of 0.18.

**Exit Ticket**

Fran is surveying a plot of land in the shape of a right triangle. The area of the land is 45,000 sq meters. If the base of the triangular plot is 0.18 km long, what is the height, in meters, of the triangle?

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- UNIT 1: First Week of School
- UNIT 2: Properties of Math
- UNIT 3: Divisibility Rules
- UNIT 4: Factors and Multiples
- UNIT 5: Introduction to Fractions
- UNIT 6: Adding and Subtracting Fractions
- UNIT 7: Multiplying and Dividing Fractions
- UNIT 8: Algorithms and Decimal Operations
- UNIT 9: Multi-Unit Summative Assessments
- UNIT 10: Rational Numbers
- UNIT 11: Equivalent Ratios
- UNIT 12: Unit Rate
- UNIT 13: Fractions, Decimals, and Percents
- UNIT 14: Algebra
- UNIT 15: Geometry

- LESSON 1: Developing the Area Formulas for Regular Polygons
- LESSON 2: Applying the Area Formulas for Regular Polygons
- LESSON 3: Area of Irregular Polygons, Method 1
- LESSON 4: Area of Irregular Polygons, Method 2
- LESSON 5: Area of Shaded Regions
- LESSON 6: Categories and Characteristics of 3D Solids
- LESSON 7: Creating and Identifying Polyhedra
- LESSON 8: Surface Area of 3D Solids
- LESSON 9: Volume of Rectangular Prism
- LESSON 10: Area of Polygons Quiz
- LESSON 11: Geometry Town Project