Perimeter Power: Cracking the Code of Rectangles and Squares!

Mathematics Grades 3rd Grade 10:17 Video
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Lesson Description

Join Ashley on an exciting adventure to master perimeter! This lesson focuses on finding the perimeter of rectangles and squares using formulas. We'll learn different ways to calculate perimeter and solve tricky word problems.

Video Resource

How to Find Perimeter, Part 2

Miacademy Learning Channel

Duration: 10:17
Watch on YouTube

Key Concepts

  • Perimeter of a rectangle (P = L + L + W + W or P = 2L + 2W)
  • Perimeter of a square (P = 4s)
  • Using formulas to solve for perimeter and missing side lengths

Learning Objectives

  • Students will be able to calculate the perimeter of a rectangle using the formulas P = L + L + W + W and P = 2L + 2W.
  • Students will be able to calculate the perimeter of a square using the formula P = 4s.
  • Students will be able to solve for a missing side length of a rectangle or square when given the perimeter and other side lengths.

Educator Instructions

  • Introduction (5 mins)
    Begin by reviewing what perimeter is: the distance around a shape. Briefly recap finding the perimeter by adding all sides, as covered in the previous video.
  • Perimeter of a Rectangle (10 mins)
    Introduce the two formulas for the perimeter of a rectangle: P = L + L + W + W and P = 2L + 2W. Explain what L (length) and W (width) represent. Work through an example problem, showing how to plug in the values into both formulas and solve. Emphasize the order of operations when using P = 2L + 2W (multiplication before addition).
  • Solving for Missing Sides (10 mins)
    Present a word problem where the perimeter of a rectangle and three sides are known, and the goal is to find the missing side. Guide students through setting up the equation and using inverse operations (subtraction) to isolate the unknown variable (missing side length).
  • Perimeter of a Square (10 mins)
    Introduce the formula for the perimeter of a square: P = 4s, where 's' is the length of one side. Explain that since all sides of a square are equal, we can simply multiply the side length by 4. Work through an example problem. Then, present a problem where the perimeter of a square is given, and students need to find the side length. Explain that they need to use division (the opposite of multiplication) to solve for 's'.
  • Practice and Wrap-up (5 mins)
    Provide students with practice problems to solve independently. Review the key concepts and formulas. Encourage students to check out the Miacademy website for more practice.

Interactive Exercises

  • Rectangle Perimeter Practice
    Provide students with drawings of rectangles with labeled side lengths. Have them calculate the perimeter using both formulas (P = L + L + W + W and P = 2L + 2W) to show that they arrive at the same answer.
  • Square Side Length Challenge
    Give students the perimeter of various squares and ask them to calculate the length of each side. Encourage them to draw the square and label the side lengths once they find the answer.

Discussion Questions

  • What is perimeter? Can you give an example of where you might use perimeter in real life?
  • Why do we have two different formulas for finding the perimeter of a rectangle?
  • What is the difference between a rectangle and a square? How does that affect how we calculate the perimeter?

Skills Developed

  • Calculating perimeter of rectangles and squares
  • Using formulas
  • Problem-solving with word problems
  • Applying inverse operations (addition/subtraction, multiplication/division)

Multiple Choice Questions

Question 1:

What is perimeter?

Correct Answer: The distance all the way around a shape.

Question 2:

Which formula can you use to find the perimeter of a rectangle?

Correct Answer: P = L + L + W + W

Question 3:

A rectangle has a length of 5 inches and a width of 3 inches. What is the perimeter?

Correct Answer: 16 inches

Question 4:

Which formula can you use to find the perimeter of a square?

Correct Answer: P = 4 x s

Question 5:

A square has a side length of 6 cm. What is the perimeter?

Correct Answer: 24 cm

Question 6:

If the perimeter of a square is 20 inches, how long is each side?

Correct Answer: 5 inches

Question 7:

What does 'L' stand for in the perimeter formula for a rectangle?

Correct Answer: Length

Question 8:

What does 'W' stand for in the perimeter formula for a rectangle?

Correct Answer: Width

Question 9:

What operation do you use to find a missing side if you know the perimeter of a square?

Correct Answer: Division

Question 10:

Which shape has four equal sides?

Correct Answer: Square

Fill in the Blank Questions

Question 1:

Perimeter is the distance all the way _______ a shape.

Correct Answer: around

Question 2:

The formula for the perimeter of a square is P = 4 x ____.

Correct Answer: s

Question 3:

If a rectangle has two sides that are 7 feet long and two sides that are 3 feet long, the perimeter is ____ feet.

Correct Answer: 20

Question 4:

All four sides of a _______ are the same length.

Correct Answer: square

Question 5:

The opposite of multiplication is ______.

Correct Answer: division

Question 6:

In the formula P = 2L + 2W, you should do the _________ first.

Correct Answer: multiplication

Question 7:

If the perimeter of a square is 32 inches, each side is ____ inches long.

Correct Answer: 8

Question 8:

A _________ has two lengths and two widths.

Correct Answer: rectangle

Question 9:

We use _______ to help us solve for a missing side.

Correct Answer: formulas

Question 10:

The answer to an addition problem is called the ____.

Correct Answer: sum

Educational Standards

3.GM.2.1:Find the perimeter of a polygon, given whole number lengths of the sides, using a variety of models. 3.N.2.2:Demonstrate fluency with multiplication facts using factors up to 10. 3.A.2.1:Use number sense with the properties of addition, subtraction, and multiplication, to find unknowns (represented by symbols) in one-step equations. Generate real-world situations to represent number sentences.

Teaching Materials

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