1. Estimating Measurements 5.1a Estimate the area of irregular shapes, angle measurement, or weight of common objects 5.2a Estimate, make and use direct and indirect measurements to describe and make comparisons

2. Estimating Measurements EXAMPLE 1 Estimate the area of this irregularly shaped figure. STRATEGY Round the side lengths to the nearest whole number and find the area of each part of the figure. Step 1: Identify the familiar figures that make up the irregular shape. Step 2: Round the side lengths. Step 3: Estimate the area of the figure. SOLUTION: The area of the figure is about 23 square centimeters.

3. Estimating Measurements EXAMPLE 2 Which of the following is the best estimate of the measure of this angle? A. 130 degrees B. 70 degrees C. 40 degrees D. 10 degrees STRATEGY Compare each choice to a 90 degree angle and 180 degree angle. Step 1: Consider Choice A. Step 2: Consider Choice B. Step 3: Consider Choice C. Step 4: Consider Choice D. SOLUTION: The best estimate of the measure of the angle is 40 degrees, Choice C.

4. Estimating Measurements EXIT TICKET

5. The Effects of Changing Dimension 5.5a Describe how a change in an object’s linear dimensions affects its perimeter and area

6. The Effects of Changing Dimension EXAMPLE 1 If the length and width of the rectangle below are doubled, how will the perimeter of the new rectangle compare with the perimeter of the original rectangle? STRATEGY Find the original perimeter and the new perimeter. Then compare. Step 1: Find the perimeter of the original rectangle. Step 2: Double the length and the width. Step 3: Find the perimeter of the new rectangle. Step 4: Compare the perimeters. SOLUTION: When the width and length of the rectangle are doubled, the perimeter of the new rectangle will be twice the perimeter of the original.

7. The Effects of Changing Dimension EXAMPLE 2 If you decrease the height of this triangle by half and keep the base the same, how will the area of the new triangle compare with the area of this triangle? STRATEGY Find the original area and the new area. Then compare. Step 1: Find the area of the original triangle. Step 2: Find the area of the new triangle. Step 3: Compare the areas. SOLUTION: When the base of a triangle remains the same and height is halved, the area of the new triangle is one half the area of the original triangle.

8. The Effects of Changing Dimension EXAMPLE 3 Square A has sides that are 5 feet long. Square B has sides that are each twice as long as those of Square A. How many times greater is the area of square B than the area of Square A? STRATEGY Find the area of each square. Then compare. Step 1: Find the area of Square A. Step 2: Find the area of Square B. Step 3: Compare the areas. SOLUTION: The area of Square B is 4 times greater than the area of Square A.

9. The Effects of Changing Dimension EXIT TICKET

10. Scale Drawings 5.2a Estimate, make, and use direct and indirect measurements to describe and make comparisons 5.3a Read and interpret scales on number lines, graphs, and maps 5.3b Select the appropriate scale for a given problem

11. Scale Drawings EXAMPLE 1 On a map, Jill measured the straight-line distance between Denver and her hometown. It is 12 centimeters. The scale on the map shows 3 centimeters = 20 kilometers. What is the actual distance from Denver to Jill’s hometown? STRATEGY Set up a proportion and solve Step 1: Write the scale equation as a ratio Step 2: Use the scale ratio to set up a proportion Step 3: Solve the proportion SOLUTION: Jill’s hometown is 80 kilometers from Denver.

12. Scale Drawings EXAMPLE 2 Loretta made a scale drawing of an elephant. What is the actual length of the elephant? STRATEGY Measure the length of the elephant. Then use the scale. Step 1: Use a ruler. Step 2: Set up a proportion. Step 3: Solve the proportion. SOLUTION: The actual length of the elephant is 12 feet.

13. Scale Drawings EXAMPLE 3 A new house will be 30 feet wide. On a blueprint of the house, the scale is ¼ inch = 1 foot. How wide is the house on the blueprint? STRATEGY Set up a proportion and solve. Step 1: Write the scale equation as a ratio. Step 2: Set up a proportion. Step 3: Solve the proportion. SOLUTION: The house is 7 ½ inches wide on the blueprint.

14. Scale Drawings EXIT TICKET