Lesson objective: Apply scale factors to find the perimeters of actual buildings given a sketch of the buildings.

This lesson provides an opportunity for students to apply their knowledge and understanding of scaled perimeters to a real-life situation. Students are asked to determine the distance walked by a night watchman given a blueprint of the buildings he guards.

Key Concept students will use:

- Lengths of sides of pairs of scale drawings are proportional, resulting in proportional perimeters.

Skills students will use:

- Scale dimensions relate to the original by a scale factor. (Grade 7, Unit 1)
- Multiplication can scale up or down (Grade 5, Unit 7)
- Dividing fractions (Grade 6, Unit 4)

Students engage in Mathematical Practice 6 (attend to precision) as they convert between inches and feet. And they also engage in Mathematical Practice 4 (Model with mathematics) as they calculate the distance in feet a night watchman walks while moving around the perimeter of buildings by studying a scale drawing of the buildings and using their knowledge of scale factors.

**Key vocabulary: **

- original figure
- proportional
- scale drawing
- scale factor