Area Explorers: Finding Missing Sides of Rectangles
Lesson Description
Video Resource
Finding missing side when given area | Math | 3rd grade | Khan Academy
Khan Academy
Key Concepts
- Area of a rectangle
- Relationship between multiplication and division
- Using formulas to solve problems
Learning Objectives
- Students will be able to calculate the area of a rectangle.
- Students will be able to identify the missing side length of a rectangle when given the area and one side length.
- Students will be able to apply multiplication and division facts to solve for the unknown side length.
Educator Instructions
- Introduction (5 mins)
Begin by reviewing what area is and how to find the area of a rectangle (Area = Length x Width). Ask students to share real-world examples of rectangles and their areas (e.g., a book cover, a classroom floor). - Video Viewing (7 mins)
Play the Khan Academy video 'Finding missing side when given area | Math | 3rd grade | Khan Academy'. Encourage students to take notes on the examples presented in the video. - Guided Practice (10 mins)
Work through a few example problems together as a class. Provide visual aids such as drawings of rectangles with the area and one side labeled. Guide students through the process of setting up the equation (Length x Width = Area) and solving for the missing side length using division. - Independent Practice (10 mins)
Provide students with a worksheet containing various problems where they need to find the missing side length of a rectangle given the area and one side. Circulate the classroom to provide support and answer questions. - Wrap-up and Assessment (8 mins)
Review the key concepts and learning objectives. Have students share their strategies for finding the missing side length. Administer the multiple-choice quiz to assess student understanding.
Interactive Exercises
- Rectangle Riddles
Present students with 'riddles' such as: 'I am a rectangle. My area is 36 square inches. One of my sides is 4 inches long. What is the length of my other side?' Have students work in pairs to solve the riddles. - Area Detective
Divide the class into teams. Give each team a set of rectangles with different measurements, some with a missing side. The teams need to find the missing side and present their solutions to the class like a detective solving a case.
Discussion Questions
- What is area and how do we measure it?
- How does knowing the area of a rectangle help us find a missing side?
- Can you think of a time when you might need to find the missing side of something in real life?
Skills Developed
- Problem-solving
- Critical thinking
- Application of mathematical concepts
Multiple Choice Questions
Question 1:
The area of a rectangle is 48 square meters. If the length is 8 meters, what is the width?
Correct Answer: 6 meters
Question 2:
A rectangle has an area of 25 square cm. If the width is 5 cm, what is the length?
Correct Answer: 5 cm
Question 3:
If a rectangle has an area of 12 square inches and a width of 3 inches, what is its length?
Correct Answer: 4 inches
Question 4:
The area of a poster is 63 square inches. One side is 9 inches. What is the length of the other side?
Correct Answer: 7 inches
Question 5:
A rug has an area of 20 square feet and a width of 4 feet. What is the length of the rug?
Correct Answer: 5 feet
Question 6:
A rectangle has an area of 30 square feet. The length is 6 feet. What is the width?
Correct Answer: 5 feet
Question 7:
What is the formula to find the area of a rectangle?
Correct Answer: Length x Width
Question 8:
A square has an area of 81 square inches. What is the length of each side?
Correct Answer: 9 inches
Question 9:
A window has an area of 24 square feet. It is 4 feet wide. How tall is the window?
Correct Answer: 6 feet
Question 10:
The classroom floor is a rectangle with an area of 350 square feet. The length of the room is 25 feet. What is the width?
Correct Answer: 15 feet
Fill in the Blank Questions
Question 1:
Area is the amount of _________ a shape covers.
Correct Answer: space
Question 2:
To find the missing side, you can ________ the area by the side you know.
Correct Answer: divide
Question 3:
If a rectangle has an area of 16 square meters and a length of 4 meters, the width is _________ meters.
Correct Answer: 4
Question 4:
The area of a rectangle is found by multiplying the ________ and the width.
Correct Answer: length
Question 5:
If you know the area and one side of a rectangle, you can find the other side using _________.
Correct Answer: division
Question 6:
A square with sides of 7 inches has an area of _______ square inches.
Correct Answer: 49
Question 7:
If the area of a rectangle is 21 square cm and the width is 3 cm, then the length is ________ cm.
Correct Answer: 7
Question 8:
Area is always measured in _________ units, like square inches or square meters.
Correct Answer: square
Question 9:
A rectangle has an area of 100 square cm. If one side is 10 cm, the other side is _______ cm.
Correct Answer: 10
Question 10:
The opposite of multiplying to find the area is _________ to find a missing side.
Correct Answer: dividing
Educational Standards
Teaching Materials
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