5.7 Scale Drawings and Models Standard: MG 1.3 Objective: Students use scales, ratios, and proportions to solve scale drawing and model problems.

Key Concepts Scale drawing: a 2D drawing of an object reduced to a proportion of the original object. Scale model: a 3D model of an object reduced to a proportion of the original object. Scale: the ratio of the dimensions of the large object to the reduced model.

Key Concept Maps, globes, Google maps, blueprints, and model cars are all examples of scale drawings and/or models. It makes it easier to understand large objects.

Example 1: Find measurement Since the distance must be proportional to the scale, write and solve a proportion to find the missing value. Make sure units match when setting up the proportion.

Practice 1 The scale on a map reads 1 cm : 200 m. Find the actual distance if the distance measured on the map is 7 cm. 5

Find the actual distance from LA to Houston. 0 300 mi Scale 1 in : 300 mi 6

Example 2: Find scale Just like in example 1, use a proportion to find the missing value.

Practice 2 A blueprint shows a house that is 15 cm long and the actual house is 75 m. The scale is 1 cm : ? m. What is the scale?

Example 3: Find dimensions First change the scale to equal units (inches) Then write and solve the proportion

The scale of the house blueprint below is to be 1 in = 8 ft. If the actual dimensions are 80 ft. by 30 ft., find the map dimensions x and y. y Scale 1 in : 8 ft x Length Width 10

Review What is a scale model or drawing? What is a scale? How do you solve scale problems? Give an example of when a scale is used.