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How many cubes with an edge length of 1 inch fill this box?
Your teacher will give you cubes that have edge lengths of inch.
Here is a drawing of a cube with edge lengths of 1 inch.
How many cubes with edge lengths of inch are needed to fill this cube?
What is the volume, in cubic inches, of a cube with edge lengths of inch? Explain or show your reasoning.
Use cubes with an edge length of inch to build prisms with the lengths, widths, and heights shown in the table.
For each prism, record in the table how many -inch cubes can be packed into the prism and the volume of the prism.
| prism length (in) |
prism width (in) |
prism height (in) |
number of -inch cubes in prism |
volume of prism (in3) |
|---|---|---|---|---|
| 1 | 1 | |||
| 2 | 1 | |||
| 2 | 2 | 1 | ||
| 4 | 2 | |||
| 5 | 4 | 2 | ||
| 5 | 4 |
Explain or show how this is true.
Lin and Noah are packing small cubes into a larger cube with an edge length of inches. Lin is using cubes with an edge length of inch, and Noah is using cubes with an edge length of inch.
Who would need more cubes to fill the -inch cube? Be prepared to explain your reasoning.
If Lin and Noah each use their small cubes to find the volume of the larger -inch cube in cubic inches, will they get the same answer? Explain or show your reasoning.
A nature center has a fish tank in the shape of a rectangular prism.
The tank is 10 feet long, feet wide, and 6 feet tall.
What is the volume of the tank in cubic feet? Show your reasoning.
If a rectangular prism has edge lengths of 2 units, 3 units, and 5 units, we can think of it as 2 layers of unit cubes, with each layer having unit cubes in it. So the volume, in cubic units, is:
To find the volume of a rectangular prism with fractional edge lengths, we can think of it as being built of cubes that have a unit fraction for their edge length. For instance, if we build a prism that is -inch tall, -inch wide, and 4 inches long using cubes with a -inch edge length, we would have:
The volume of the prism would be , which is 24 cubic units.
How do we find its volume in cubic inches? We know that each cube with a -inch edge length has a volume of cubic inch, because . Since the prism is built using 24 of these cubes, its volume, in cubic inches, would then be , which is 3 cubic inches.
The volume of the prism, in cubic inches, can also be found by multiplying the fractional edge lengths in inches:
If a rectangular prism has edge lengths units, units, and units, the volume is the product of , , and .
This means that if we know the volume and two edge lengths, we can divide to find the third edge length.
Suppose the volume of a rectangular prism is cm3, one edge length is cm, another is cm, and the third edge length is unknown. We can write a multiplication equation to represent the situation:
We can find the third edge length by dividing: