options: Apply geometric concepts in modeling situations.

Understand congruence and similarity using physical models, transparencies, or geometry software.

Understand congruence in terms of rigid motions.

Reason with shapes and their attributes.

Understand similarity in terms of similarity transformations.

Explain volume formulas and use them to solve problems.

Prove theorems involving similarity.

Understand and apply theorems about circles.

Apply trigonometry to general triangles.

Solve real-world and mathematical problems involving volume of cylinders, cones, and spheres.

Draw and identify lines and angles, and classify shapes by properties of their lines and angles.

Understand and apply the Pythagorean Theorem.

Make geometric constructions.

Visualize relationships between two-dimensional and three-dimensional objects.

Define trigonometric ratios and solve problems involving right triangles.

Draw, construct, and describe geometrical figures and describe the relationships between them.

Solve real-life and mathematical problems involving angle measure, area, surface area, and volume.

Prove geometric theorems.

Translate between the geometric description and the equation for a conic section.

Analyze, compare, create, and compose shapes.

Experiment with transformations in the plane.

Find arc lengths and areas of sectors of circles.

Use coordinates to prove simple geometric theorems algebraically.

Solve real-world and mathematical problems involving area, surface area, and volume.

Identify and describe shapes (squares, circles, triangles, rectangles, hexagons, cubes, cones, cylinders, and spheres).

Classify two-dimensional figures into categories based on their properties.

Graph points on the coordinate plane to solve real-world and mathematical problems.
problem_activity: Activity
In this activity, students continue the work on finding the volume of a right rectangular prism with fractional edge lengths. This time, they do so by packing it with unit cubes of different unit fractions for their edge lengths—
\(\frac13\)
,
\(\frac12\)
, and
\(\frac14\)
of an inch. They use these cubes to find the volume of the prism in cubic inches, decide which unit fraction works better to accomplish this goal and why, and explain whether cubes of different fractional edge lengths would lead to the same volume in cubic inches (MP3).
As students work, notice those who are able to clearly explain why cubes with a particular fractional edge length are preferable as a unit of measurement and why the volume in cubic inches will be the same regardless of the cubes used. Invite them to share later.
Launch
Arrange students in groups of 3–4. Give them 8–10 minutes of quiet work time, and then 5 minutes to discuss their responses with their group. Ask groups to be sure to discuss the third question. Encourage students to draw a sketch to help with reasoning, if needed.
Representation: Internalize Comprehension
. Activate or supply background knowledge about measurement. Students may benefit from watching a quick demonstration or video of packing cubes into a box. Review terms such as dimensions, volume, and cubic units.
Supports accessibility for: Memory; Conceptual processing
Student Facing
Diego says that 108 cubes with an edge length of
\(\frac13\)
inch are needed to fill a rectangular prism that is 3 inches by 1 inch by
\(1\frac13\)
inch.
Explain or show how this is true. If you get stuck, consider drawing a diagram.
What is the volume, in cubic inches, of the rectangular prism? Explain or show your reasoning.
Lin and Noah are packing small cubes into a larger cube with an edge length of
\(1\frac12\)
inches. Lin is using cubes with an edge length of
\(\frac12\)
inch, and Noah is using cubes with an edge length of
\(\frac14\)
inch.
Who would need more cubes to fill the
\(1\frac12\)
-inch cube? Be prepared to explain your reasoning.
If Lin and Noah each use their small cubes to find the volume of the larger
\(1\frac12\)
-inch cube, will they get the same answer? Explain or show your reasoning.
Student Response
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Anticipated Misconceptions
If students have trouble getting started, ask them to revisit their work with
\(\frac12\)
-inch cubes from a previous lesson. Remind them that a cube with
\(\frac 12\)
-inch edge length has a volume of
\(\frac18\)
in
3
(because we can fit 8 of such cubes in a 1-inch cube). Ask them to think about how many
\(\frac13\)
-inch cubes can fit into a 1-inch cube, or think about what the volume of a
\(\frac13\)
-inch cube is in cubic inches.
Some students may not be able to visualize and keep track of the measurements of the boxes in this task. Encourage students to draw and label the measurements of the boxes described in these questions.
Activity Synthesis
Select several students to share their responses and articulate their reasoning. Compare the different strategies students used for finding the volume of the rectangular prism. Ask students:
“Does it matter which fractional-unit cubes we use to find the volume? Why or why not?” (As long as the unit fraction can fit evenly into all three edge lengths of the prism, it doesn’t matter what unit fraction we use.)
“Do certain unit fractions work better as edge lengths of the small cubes than others?” (It helps to use as large a unit fraction as possible, since it means using fewer cubes and working with fractions that are closer to 1.)
“Is there another way of finding the volume of a rectangular prism with fractional edge length besides using these small cubes?” (Multiply the fractional edge lengths.)
Point out that it is helpful to use a unit fraction that is a common factor of the fractional edge lengths of the prism. Make sure students also recognize that multiplying the edge lengths of the prism is a practical way to find the volume of such a rectangular prism.


correct_option_index: 23