# PSAT Math : Cubes

## Example Questions

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### Example Question #1 : How To Find The Length Of An Edge Of A Cube

If the volume of a cube is 64 cubic inches, then it has an edge length of _______.

9 in

8 in

6 in

4 in

2 in

4 in

Explanation:

### Example Question #1 : How To Find The Length Of An Edge Of A Cube

If the volume of a cube is 512 units, what is the length of one edge of the cube?

Explanation:

The volume of a cube is length x width x height. Since it's a cube, though, the length, width, and height are all equal, and equivalent to the length of one edge of the cube.  Therefore, to find the lenght of an edge of the cube, just find the cube root of the volume. In this case, the cube root of 512 is equal to 8.

### Example Question #3 : How To Find The Length Of An Edge Of A Cube

Find the length of an edge of a cube that has a volume of .

Explanation:

All the edges of a cube have the same length, and the volume of a cube is the length of an edge taken to the third power.

So if we take the edge of the cube to be of length x, then:

So the length of the edge of a cube with a volume of 125 is 5.

### Example Question #4 : How To Find The Length Of An Edge Of A Cube

A certain shipping company has cubic boxes. One of these boxes has a volume of . How long are each of the sides of the box in feet?

Explanation:

The formula for the volume of a cube is

where  is the length of a side.

Here, the volume is 729. To find the side length, take the cube root of both sides:

The cube root of 729 is 9, so the length of each side of the cube is 9 feet.

### Example Question #5 : How To Find The Length Of An Edge Of A Cube

If a cube has a volume of   cubic inches, approximately how long, in feet, is one edge of the cube?