Perimeter Puzzle: Cracking the Missing Side Code!
Lesson Description
Video Resource
Finding missing side length when given perimeter | Math | 3rd grade | Khan Academy
Khan Academy
Key Concepts
- Perimeter is the total distance around a shape.
- The sum of all side lengths equals the perimeter.
- Missing side lengths can be found by subtracting the known side lengths from the total perimeter.
Learning Objectives
- Students will be able to define perimeter.
- Students will be able to calculate the missing side length of a polygon when given the perimeter and other side lengths.
- Students will be able to apply addition and subtraction skills to solve real-world perimeter problems.
Educator Instructions
- Introduction (5 mins)
Begin by reviewing what perimeter is. Ask students to describe in their own words what perimeter means. Use real-world examples like the fence around a yard or the border of a classroom bulletin board. - Video Viewing (7 mins)
Play the Khan Academy video: 'Finding missing side length when given perimeter | Math | 3rd grade | Khan Academy'. Instruct students to pay attention to how Lindsay solves for the missing side length in different shapes. - Guided Practice (10 mins)
Work through the examples from the video together as a class. Pause the video at key points to ask guiding questions, such as 'What do we know?' and 'What are we trying to find?' Model the steps to solve each problem, emphasizing the importance of addition and subtraction. - Independent Practice (10 mins)
Provide students with worksheets or online activities where they can practice finding missing side lengths on their own. Include a variety of shapes and perimeters to challenge students. - Wrap-up and Assessment (8 mins)
Review the key concepts of the lesson. Have students share their strategies for solving perimeter problems. Administer a short quiz to assess student understanding.
Interactive Exercises
- Perimeter Puzzles
Provide students with puzzle pieces representing different shapes with some side lengths labeled and the perimeter given. Students must calculate the missing side length to complete the puzzle. - Shape Scavenger Hunt
Students find objects in the classroom or at home that are shaped like polygons. They estimate the side lengths, then measure them to find the perimeter. They then remove one side length and recalculate what the missing side length would be if they only knew the total perimeter.
Discussion Questions
- What is perimeter, in your own words?
- How can you use addition to help you find a missing side length?
- How can you use subtraction to help you find a missing side length?
- What strategies did you use to solve for the missing side length?
Skills Developed
- Problem-solving
- Addition and Subtraction
- Measurement
- Analytical thinking
Multiple Choice Questions
Question 1:
What is the perimeter of a shape?
Correct Answer: The distance around the outside of the shape.
Question 2:
A rectangle has a perimeter of 20 cm. Three of its sides are 3 cm, 7 cm, and 3 cm. What is the length of the missing side?
Correct Answer: 7 cm
Question 3:
A triangle has sides of 5 inches and 7 inches. If the perimeter is 18 inches, what is the length of the third side?
Correct Answer: 6 inches
Question 4:
A square has a perimeter of 24 meters. What is the length of each side?
Correct Answer: 6 meters
Question 5:
If you know the perimeter of a shape and the length of all but one side, how do you find the missing side length?
Correct Answer: Subtract all the known sides from the perimeter.
Question 6:
A shape has sides measuring 2cm, 4cm, 6cm, and 8cm. What is the perimeter of the shape?
Correct Answer: 20 cm
Question 7:
What is the length of a side of an equaliteral triangle when given a perimiter of 30 feet?
Correct Answer: 10 feet
Question 8:
John measured a square and found one side to be 7cm long. If he finds the perimiter what length should he find?
Correct Answer: 28cm
Question 9:
The perimiter of a yard is 46ft. One side is 10 ft, another is 5 ft, and a third is 15 ft. What is the length of the missing side?
Correct Answer: 16 ft
Question 10:
A farmer wants to build a fence around his pen. The perimiter of his pen is 100 ft. The pen is rectangular with one side 30 ft and another side 20 ft. What is the length of the remaining two sides?
Correct Answer: 25 ft, 25 ft
Fill in the Blank Questions
Question 1:
The distance around the outside of a shape is called the ________.
Correct Answer: perimeter
Question 2:
To find a missing side length, you can ________ the known side lengths from the total perimeter.
Correct Answer: subtract
Question 3:
A square has four equal ________.
Correct Answer: sides
Question 4:
If a rectangle has a perimeter of 30 cm and one side is 8 cm, the opposite side is also ________ cm.
Correct Answer: 8
Question 5:
Perimeter is measured in units like centimeters, meters, inches, or ________.
Correct Answer: feet
Question 6:
The perimeter of a rectangle is 50 inches. If one side is 15 inches, then the other side must be _____ inches
Correct Answer: 10
Question 7:
John walked around the outside of a square. If the perimiter of the square was 20 ft, then each side was _______ feet long.
Correct Answer: 5
Question 8:
An ________ triangle has 3 congruent sides.
Correct Answer: equaliteral
Question 9:
The perimiter of a pentagon is 100 ft. If each side is of equal length, then one side is _______ feet.
Correct Answer: 20
Question 10:
To find the perimiter of an object, you must _______ the total length of each side.
Correct Answer: add
Educational Standards
Teaching Materials
Download ready-to-use materials for this lesson:
User Actions
Related Lesson Plans
-
Unlocking the Magic of Least Common Multiple (LCM)4th Grade · Mathematics -
Finding the Biggest Buddies: Understanding Greatest Common Factor (GCF)4th Grade · Mathematics -
Multiply and Divide Like a Math Magician!4th Grade · Mathematics -
Cupcakes and Calculations: Mastering Long Multiplication!4th Grade · Mathematics