Every inch of length of his model is representative of 25 inches in the actual car. So if the the actual car was 25 inches long, the model would be 1 inch long. The means the ratio of length is 0.04. You take that number, and multiply it by length of the actual car. 0.04 x 193.75 inches = 7.75 inches. The length of the model car is 7.75 inches.