We are asked to evaluate the scale factor of a scale model of a car to the actual car. Since the scale factor is a unitless ratio, we will start with expressing the actual length of the car only in inches. Recall that there are 12 inches in one foot.
10ft6in.=10* 12in.+6in.=126in.
Now, we will create a ratio using the fact that the length of the model is 7 inches.
7/126=1/18
The scale factor of the model to the actual car is 1:18.
