Examples
Example: Mike is having a graduation party and wants to make sure he has enough pizza. Which option would provide more pizza for his guests: one 12-inch pizza or three 6-inch pizzas?Benchmark Instructional Guide
Connecting Benchmarks/Horizontal Alignment
Terms from the K-12 Glossary
- Area
- Scale Factor
- Scale Model
Vertical Alignment
Previous Benchmarks
Next Benchmarks
Purpose and Instructional Strategies
In middle grades, students learned about scale drawings and scale factors. In Geometry, students use that previous knowledge to learn about how changes in the dimensions of a figure due to a dilation will affect the area of two-dimensional figures and the surface area or volume of three-dimensional figures in a way they can predict. (MTR.2.1) This understanding will be valuable to students in science courses.- Instruction includes exploring the effect of changing the dimensions of two-dimensional
and three-dimensional figures using different factors. It may be helpful to begin exploring
through specific problems working with a table of values or with algebraic formulas.
- For example, have students explore what happens to the area of a rectangle if the height is doubled and the length is tripled. Additionally, have them explore what happens to the volume of a cylinder if the height is multiplied by 0.5 and the radius is multiplied by 4.
- Instruction includes reviewing that the area of the image of a dilation with scale factor is 2 times the area of the pre-image for any two-dimensional figure (as this was done in grade 7).
- Instruction includes the student understanding that the surface area of the image of a dilation with scale factor is 2 times the surface area of the pre-image, and the volume of the image of a dilation with scale factor is 3 times the volume of the pre-image for any three-dimensional figure.
Common Misconceptions or Errors
- Students may multiply the area, surface area or volume by the scale factor instead of thinking about the multiple dimensions.
- Students may believe the scale factor has the same effect on surface area and volume. To help address this, discuss the effects on surface area using two-dimensional nets of simple figures and then compare to the effects on volumes.
Instructional Tasks
Instructional Task 1 (MTR.4.1, MTR.5.1)- Use the table below to answer the following questions.
- Part A. Determine the surface area and volume of the square pyramid.
- Part B. Given the three different dilations, or scale factors, determine the new surface areas and volumes.
- Part C. Compare each of the new surface areas to the original surface area. Compare each of the new volumes to the original volume.
- Part D. Predict the surface area and volume of the square pyramid resulting from a dilation with a scale factor of 5? Explain the method you choose..
Instructional Items
Instructional Item 1- The perfume Eau de Matimatica is packaged in a triangular prism bottle. The dimensions of the travel size are 1/3 the dimensions of the standard bottle. How does the volume of the standard bottle compare to the travel size?
Related Courses
Related Access Points
Related Resources
Lesson Plans
Perspectives Video: Professional/Enthusiasts
STEM Lessons - Model Eliciting Activity
Students use measures and properties of rectangular prisms and cylinders to model and rank 3D printable designs of interchangeable wristwatch bands that satisfy physical constraints.
Model Eliciting Activities, MEAs, are open-ended, interdisciplinary problem-solving activities that are meant to reveal students’ thinking about the concepts embedded in realistic situations. Click here to learn more about MEAs and how they can transform your classroom.
"Poly Wants a Bridge" is a model-eliciting activity that allows students to assist the city of Polygon City with selecting the most appropriate bridge to build. Teams of students are required to analyze properties of bridges, such as physical composition and span length in order to solve the problem.
Model Eliciting Activities, MEAs, are open-ended, interdisciplinary problem-solving activities that are meant to reveal students’ thinking about the concepts embedded in realistic situations. Click here to learn more about MEAs and how they can transform your classroom.
Student Resources
Perspectives Video: Professional/Enthusiasts
<p>Don't be a shrinking violet. Learn how uniform scaling is important for candy production.</p>
Type: Perspectives Video: Professional/Enthusiast
<p>You'll need to bring your computer skills and math knowledge to estimate oil volume and rate as it seeps from the ocean floor. Dive in!</p>
Type: Perspectives Video: Professional/Enthusiast
Parent Resources
Perspectives Video: Professional/Enthusiasts
<p>Don't be a shrinking violet. Learn how uniform scaling is important for candy production.</p>
Type: Perspectives Video: Professional/Enthusiast
<p>You'll need to bring your computer skills and math knowledge to estimate oil volume and rate as it seeps from the ocean floor. Dive in!</p>
Type: Perspectives Video: Professional/Enthusiast