Volume measures the three-dimensional space occupied by a solid, expressed as the number of unit cubes needed to fill it without gaps or overlaps. For rectangular prisms, learners interpret layers of congruent cubes and connect the count to , distinguishing cubic units from square units and recognizing that changing any dimension changes the volume proportionally. This scope focuses on whole-unit-cube models and rectangular prisms, not fractional cubes or more advanced composite solids.
Volume tells how much space a solid takes up. We can find the volume of a rectangular prism by counting the unit cubes that fill it.
A unit cube has side lengths of 1 unit. Its volume is 1 cubic unit.
For a rectangular prism:
where is length, is width, and is height.
Example: A rectangular prism is filled with cubes. It is 4 cubes long, 3 cubes wide, and 2 cubes high. What is its volume?
There are 12 cubes in each layer.
There are 2 layers, so multiply by the height:
Or use the volume formula:
The answer uses cubic units because we are measuring the space filled by three-dimensional cubes. Square units measure flat area, not volume.
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