In this lesson, students see that a scale can be expressed without units. For example, the scale “1 to 60” means that every length on the scale drawing represents an actual length that is 60 times its size, whatever the unit may be (inches, centimeters, etc.).

Expressing the scale without units, such as “1 to 60,” highlights the scale factor that relates the scale drawing to the actual object. Each measurement on the scale drawing is multiplied by 60 to find the corresponding measurement on the actual object. This relates closely to the scaled copies that were examined earlier in the unit in which each copy was related to the original by a scale factor. Students gain a better understanding of both scaled copies and scale drawings as they recognize the common underlying structure (MP7).