Final answer:
To calculate the actual length of the building from the scale model, multiply the scale model length (15 inches) by the inverse of the scale factor (20), and then convert inches to feet. The building is 25 feet long.
Step-by-step explanation:
The question asks us to determine the actual length of a building given that the scale model is 15 inches long with a scale factor of 1/20. To find the actual length, we multiply the length of the scale model by the inverse of the scale factor, which is 20/1. Therefore, the actual length of the building is 15 inches * 20 = 300 inches. Since there are 12 inches in a foot, we then convert inches to feet, resulting in 300 inches / 12 inches per foot = 25 feet. Thus, the actual length of the building is 25 feet.