Curriculum / Math / 3rd Grade / Unit 5: Shapes and Their Perimeter / Lesson 11
Math
Unit 5
3rd Grade
Lesson 11 of 16
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Lesson Notes
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Find side lengths of regular polygons and of rectangles when given perimeter and other side lengths.
The core standards covered in this lesson
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.
The foundational standards covered in this lesson
3.OA.D.8 — Solve two-step word problems using the four operations. Represent these problems using equations with a letter standing for the unknown quantity. Assess the reasonableness of answers using mental computation and estimation strategies including rounding. This standard is limited to problems posed with whole numbers and having whole-number answers; students should know how to perform operations in the conventional order when there are no parentheses to specify a particular order (Order of Operations).
The essential concepts students need to demonstrate or understand to achieve the lesson objective
Suggestions for teachers to help them teach this lesson
This and the next lesson can be consolidated if you are tight on time. To do so, use Anchor Tasks 1 and 3 from this lesson and Anchor Task 1 from the next lesson. Then combine their Problem Sets, Target Tasks, and Extra Practive Problems to cover the content of both lessons equitably.
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Tasks designed to teach criteria for success of the lesson, and guidance to help draw out student understanding
25-30 minutes
The shape below has a perimeter of 48 meters.
What is the length, in meters, of the unknown side?
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The following shape is a regular pentagon. Its perimeter is 45 yards. What is the length of one side of the pentagon?
The perimeter of the following rectangle is 56 centimeters. What is the rectangle’s length?
15-20 minutes
Problem Set
A task that represents the peak thinking of the lesson - mastery will indicate whether or not objective was achieved
5-10 minutes
The shape below has a perimeter of 30 feet.
What is the length of the side that is missing a number?
Tessa ropes off a rectangular part of her lawn to create a play area for her dog. She uses 32 yards of rope. What is the missing side length of the play area?
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.
Extra Practice Problems
Help students strengthen their application and fluency skills with daily word problem practice and content-aligned fluency activities.
Next
Solve more complex word problems involving perimeter, such as finding a missing side length given perimeter and other side lengths.
Topic A: Attributes of Two-Dimensional Shapes
Compare and classify polygons.
Standards
3.G.A.1
Compare and classify quadrilaterals.
Draw shapes with specified attributes.
Reason about composing and decomposing polygons using tangrams.
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Topic B: Understanding Perimeter
Understand perimeter to be the boundary around a two-dimensional shape. Compare perimeters of various polygons using concrete non-standard units.
3.MD.D.8
Find perimeter of polygons whose sides are marked with unit length marks by counting the unit lengths.
Find perimeter of shapes with all side lengths labeled.
Find perimeter by measuring side lengths in whole number units.
Find perimeter of regular polygons and of rectangles when some side lengths are not given.
Solve word problems involving finding perimeter given the side lengths.
Topic C: Distinguishing Between Area and Perimeter
Find rectangles with the same area and different perimeters.
Find rectangles with the same perimeter and different areas.
Solve a variety of word problems involving area and perimeter.
Reason about composing and decomposing polygons with various areas and perimeters using tetrominoes.
3.G.A.13.MD.D.8
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