My Inspiration

Volume is measured in cubes, hence the label cubic units.  This concept is easy to visualize when building structures with 1 in³ cubes or when calculating the volume of a rectangular prism.  A cube is a special type of rectangular prism built with, 6 sides, straight edges and right angles.

Things change when finding the volume of 3-dimensional objects with curved sides, such as a cylinder.  Conceptually understanding that the volume of a cylinder is still measured in cubes pushes against students’ preconceived notions about volume.   How can you fit a bunch of cubes perfectly into a cylinder?!?!?

When I taught this concept, I’d use examples such as containers of refried beans or Play-Doh. We discussed that if we scraped out all the beans or Play-Doh and then formed them into cubes, the number of cubes created would equal our calculated answer.  (Give or take depending on measurements and container construction).  It’s possible to then squish and jam the cubes back into the container where the beans or Play-Doh would fit compactly.

Seeing is Believing

By connecting the volume of a cylinder with a pliable material like Play-Doh, the students were able to create a picture in their minds.  They now had a visual to reference.  After my exposure with Dan Meyer’s 3 act math concept, I knew I could build students’ capacity to understand volume through a 3 act math lesson.  The goal of the lesson would be to prove the volume calculations by taking the contents of a Play-Doh container and forming it into cubes – Therefore, providing a physical model to reference.

The 3 Act

Grade 8 Standard:  G.C.9:   Volume of a cylinder:

• Act 1
• Act 2
•   

Dan Meyer inquired about the radius of the sphere, so I included this picture.  If you’re discussing the volume of a sphere, you may want this information.

• Act 3 

You can download the lesson from Dan Meyer’s Website:

• My 3-Act Lesson:  Play-Doh Cubes
• Dan’s website:  101qs.com

Shout Outs

Thanks go out to my colleagues Mariko Arteaga and J.J. Martinez.  Mari helped create the cubes.  J.J. came on board with the stop motion idea.

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Other Resources:

Blog Post: Designing & Implementing a 3-Act Lesson: The Drumstick Dash

List of my other 3-act lessons:  3 Act Lessons

Link to my Desmos Page:  Desmos Activities

My latest posts:

• The Zeroth Power: Desmos & VNPS
• Why Do We Invert & Multiply? An Explanation