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K-5 Grade 3 Unit 7 Lesson 8

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Lesson 8

Warm-up Activity 1 Activity 2

Unit 7, Lesson 8

Find the Perimeter

Grade 3

Warm-up

Number Talk: Decreasing Dividend

Find the value of each expression mentally.

Activity 1

Ways to Find Perimeter

What do you notice? What do you wonder?

Diagram. 2 rectangles. One on a 5 by 3 dot grid, one with sides marked 5 and 3.

Find the perimeter of each shape. Explain or show your reasoning.

Activity 2

Something Is Missing

Find the perimeter of this rectangle. Explain or show your reasoning.
All the short sides of this figure are the same length, and all the angles are right angles. Find the perimeter of the figure. Explain or show your reasoning.
This octagon has all equal side lengths. Find the perimeter of the octagon. Explain or show your reasoning.

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Standards Alignment

Building On

Addressing

3.OA.7

Fluently multiply and divide within 100, using strategies such as the relationship between multiplication and division (e.g., knowing that 8 × 5 = 40, one knows 40 ÷ 5 = 8) or properties of operations. By the end of Grade 3, know from memory all products of two one-digit numbers.

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Building Toward

Standards Alignment

Building On

Addressing

3.MD.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.

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Building Toward

Standards Alignment

Building On

Addressing

3.MD.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.

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Building Toward