Learn about Scale Factor in Ratios and Proportion The lesson covers the scale factor and the problem given to us is a relatively simple one, a straight forward one. It says for us to identify the scale factor when the length and inches of the race car in actual life and the model are given to us. Actual length is 132 inches and the length in the model is 12 inches. So, what are we given? We are given the actual length of the race car equals 132 inches, I get that from here. The model length of the race car equals 12 inches. We are to find the scale factor. What is the scale factor? So, the scale factor is a ratio. First, we need to know that it is a ratio which compares the measurements on a drawing or a model to the measurements of the real object. Now that we know what a scale factor is, it is simply a ratio that compares the measurements on a drawing to that of a real object. So in this case, the scale factor is what do we know? What's the measurement of the drawing on a model? Well, that is 12 inches, the ratio of 12 inches to the measurement of the real object which is 132 inches. I can also write a ratio as 12/132. It’s the same thing I can write it as 12:132 or 12/132 of course inches on both sides. And I can write this in simplest form. In order to write this in simplest form, I divide 12 by 12 and 132 by 12, 12 is the greatest common factor for 12 and 132 which gives me 1/132 divided by 12 is 11. So, the scale factor for this particular model of race car to the actual length is 1/11. That’s what we’re looking for. Quickly recapping, all we did was look at the actual length and the model length. Scale factor is the ratio between the model or drawing length to the actual length. So, if the ratio is 12:132, which when I put in simplest terms divided by GCF, we get 1/11.