If the perimeter of a rectangle is 30 units and the length is 10 units, what is the width?

To determine the width of the rectangle when given its perimeter and length, you can use the formula for the perimeter of a rectangle. The formula is:

[ P = 2L + 2W ]

where ( P ) is the perimeter, ( L ) is the length, and ( W ) is the width. In this scenario, the perimeter is 30 units and the length is 10 units.

Substituting the known values into the formula gives:

[ 30 = 2(10) + 2W ]

This simplifies to:

[ 30 = 20 + 2W ]

Next, isolate the term involving the width:

[ 30 - 20 = 2W ]

[ 10 = 2W ]

Dividing both sides by 2 results in:

[ W = 5 ]

Thus, the width of the rectangle is 5 units. This calculation confirms that the correct choice accurately represents the dimensions based on the perimeter provided.