# Understanding Three-Dimensional Figures

Videos and lessons with examples and solutions to help Grade 7 students learn how to describe three-dimensional figures built from cubes by looking at horizontal slicing planes.

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### Lesson 19 Student Outcomes

• Students learn to describe three-dimensional figures built from cubes by looking at horizontal slicing planes.
• Students describe three-dimensional figures built from cubes by looking at horizontal slicing planes

### Lesson 19 Summary

• This lesson takes a different perspective of three-dimensional figures built from unit cubes by examining the horizontal whole-unit slices. The slices allow a way to count the number of unit cubes in the figure, which is particularly useful when the figure is layered in a way so that many cubes are hidden from view.

Lesson 19 Classwork

Example 1
If slices parallel to the tabletop (with height a whole number of units from the tabletop) were taken of this figure, then what would each slice look like?

Example 2
If slices parallel to the tabletop were taken of this figure, then what would each slice look like?

Exercise 1
Based on the level slices you determined in Example 2, how many unit cubes are in the figure?

Exercise 2
a. If slices parallel to the tabletop were taken of this figure, then what would each slice look like?
b. Given the level slices in the figure, how many unit cubes are in the figure?

Example 3
Given the level slices in the figure, how many unit cubes are in the figure?

Exercise 3
Sketch your own three dimensional figure made from cubes and the slices of your figure. Explain how the slices relate to the figure.

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