Shapes and Their Perimeter

Lesson 15

Math

Unit 5

3rd Grade

Lesson 15 of 16

Objective


Solve a variety of word problems involving area and perimeter.

Common Core Standards


Core Standards

  • 3.MD.D.8 — Solve real world and mathematical problems involving perimeters of polygons, including finding the perimeter given the side lengths, finding an unknown side length, and exhibiting rectangles with the same perimeter and different areas or with the same area and different perimeters.

Foundational Standards

  • 3.MD.C.5
  • 3.MD.C.6
  • 3.MD.C.7
  • 3.OA.D.8

Criteria for Success


Solve word problems involving area and perimeter, including given the length and width of a rectangle, determine its area and perimeter; given the area and one dimension of a rectangle, determine its perimeter; and given the perimeter and one dimension of a rectangle, determine its area (MP.4).

Tips for Teachers


Students solve word problems involving both perimeter and area in this lesson, thus connecting the additional cluster content of perimeter to the major cluster content of area.

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Anchor Tasks

25-30 minutes


Problem 1

Claudia is redecorating her bedroom, which is in the shape of a rectangle that is 8 feet long and 9 feet wide. She needs to buy new carpeting and wants to put baseboards around the border of her bedroom. 

a.   How much carpeting should Claudia order?

b.   How much baseboard should Claudia order?

Guiding Questions

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Student Response

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Problem 2

The length of a rectangle is 6 cm and its perimeter is 16 cm. What is the area of the rectangle in square centimeters?

Guiding Questions

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Student Response

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Problem Set

15-20 minutes


Discussion of Problem Set

  • How was it helpful to have the first few questions broken down into several parts?
  • Explain to a partner how knowing the area and the width helped you find the length of the rectangle in #3.
  • How did you know you needed to add the areas of three paintings in #3(c)?
  • How did you find the width of the rectangle in #4(a)?
  • How many rabbits could Patsy place in the playpen with the largest area in #5(c)? How did you solve?
  • Which problem did you find most difficult? Why?

Target Task

5-10 minutes


Problem 1

The area of a rectangular bulletin board is 20 square feet. The length of the bulletin board is 5 feet. What is the perimeter of the bulletin board?

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Student Response

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Problem 2

Mrs. Rothschild wants to put up a new bulletin board outside of her classroom. She wants the bulletin board to be 4 feet tall and 7 feet long. The bulletin board will be covered with cork and will have a metal frame around it. 

a.   How much metal framing does Mrs. Rothschild need?

b.   How much cork does Mrs. Rothschild need? 

Student Response

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Additional Practice


The Extra Practice Problems can be used as additional practice for homework, during an intervention block, etc. Daily Word Problems and Fluency Activities are aligned to the content of the unit but not necessarily to the lesson objective, therefore feel free to use them anytime during your school day.

Word Problems and Fluency Activities

Word Problems and Fluency Activities

Help students strengthen their application and fluency skills with daily word problem practice and content-aligned fluency activities.

Next

Reason about composing and decomposing polygons with various areas and perimeters using tetrominoes.

Lesson 16
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Lesson Map

A7CB09C2-D12F-4F55-80DB-37298FF0A765

Topic A: Attributes of Two-Dimensional Shapes

Topic B: Understanding Perimeter

Topic C: Distinguishing Between Area and Perimeter

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