Final answer:
The width of a rectangle cannot be determined only by knowing its length; additional information such as the rectangle's area is needed to calculate the width.
Step-by-step explanation:
If the length of a rectangle is 30 inches, determining the width of the rectangle depends on additional information such as the area of the rectangle or the perimeter. Without such information, the question cannot be answered definitively. If we know the area of the rectangle, the width can be calculated by dividing the area by the length.
For example, if the area was 60 square inches, then the width would be the area (60) divided by the length (30), giving us 2 inches for the width. The answer to the original student's question would be (c) Depends on the rectangle's area.