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The length scale factor of a scale drawing or scale model is the ratio of a length on the drawing or model to the corresponding actual length where both lengths have the same units of measure.
Length scale factor = Length on model/Actual length
Since it is a ratio, the length scale factor can also be written using colon notation. However, it is usually written as a constant that describes the relationship between the dimensions of the scale drawing or scale model and the actual dimensions.
The length scale factor definition also applies for similar figures. Examine these two similar triangles.
The length scale factor used to get △ PQR from △ ABC is the ratio between a measure on the new figure, △ PQR, and the corresponding measure on the initial figure, △ ABC. Here, PR and AC are corresponding sides. Therefore, the length scale factor is the ratio between PR and AC. Length scale factor &= PR/AC = 5/2.5 &⇓ Length scale factor &= 2 Every side length in △ PQR is twice the corresponding side length in △ ABC. Notice that the length scale factor for getting △ ABC from △ PQR is 12.