Final answer:
The resulting unit when multiplying length by width in inches is square inches (in²), which measures area in a two-dimensional space.
Step-by-step explanation:
When multiplying a length in inches by a width in inches, the resulting answer will be in the unit measurement of square inches (in²). This is because you are calculating an area which is a two-dimensional measurement. The multiplication of the dimensions in inches gives you the total area in square inches. The other units listed, such as ft², cm³, ft, m², and ft³, are not applicable as they represent different measurement units or are related to volumes (three-dimensional measurements), not area.