1. 3rd Grade Math Module 7 Lesson 20
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3rd Grade Math
Module 7 Lesson 20

2. Lesson 20 Learning Goal
I can construct rectangles with a given perimeter and determine their areas.

3. Lesson 20
I can construct rectangles with a given
perimeter and determine their areas.
Molly builds a rectangular playpen for her pet rabbit. The playpen has an area of 15 square yards.
Draw as many possible models as you can for the playpen.
Find the perimeter of each playpen.
What other information would you need to recreate Molly’s playpen?
Application Problem

4. Lesson 20
I can construct rectangles with a given
perimeter and determine their areas.
Molly builds a rectangular playpen for her pet rabbit. The playpen has an area of 15 square yards.
Draw as many possible models as you can for the playpen.
Find the perimeter of each playpen.
What other information would you need to recreate Molly’s playpen?
15 yd
1 yd M
The perimeter of playpen M is 32 yards.
= 32 yds
The perimeter of playpen N is 16 yards.
= 16 yds
To recreate Molly’s playpen, I need to know the perimeter or the side-lengths.
5 yd N
3 yd
Application Problem

5. Lesson 20
I can construct rectangles with a given
perimeter and determine their areas.
Problem Set:
How is problem 1 different from the work we’ve been doing in the last few lessons?
What strategies might we use to help us when we know the perimeter?
How does the equation represent the perimeter of the rectangle?
8 cm
3 cm
3 cm
8 cm
P = 2 x (3 + 8)
Concept Development

6. Solve the addition fact and rewrite the equation using the sum.
Lesson 20
I can construct rectangles with a given
perimeter and determine their areas.
8 cm
3 cm
3 cm
8 cm
P = 2 x (3 + 8)
Solve the addition fact and rewrite the equation using the sum.
Concept Development

7. Lesson 20 P = 2 x 11 When we multiply a number by 2,
I can construct rectangles with a given
perimeter and determine their areas.
8 cm
3 cm
3 cm
8 cm
P = 2 x 11
When we multiply a number by 2,
what are we doing to that number?
Concept Development

8. Lesson 20 P = 2 x 11 Can the perimeter of all rectangles be written as
I can construct rectangles with a given
perimeter and determine their areas.
8 cm
3 cm
3 cm
8 cm
P = 2 x 11
Can the perimeter of all rectangles be written as
double the sum of the width and length?
Concept Development

9. Use Problem Set to continue
Lesson 20
I can construct rectangles with a given
perimeter and determine their areas.
Use Problem Set to continue
Concept Development.
Concept Development