Calculating Perimeter Using Scale Factors and Proportions

This video tutorial teaches how to calculate the perimeter of a shape using scale drawings, ratios, and proportions. It explains the concept of proportions, demonstrates the cross multiplication technique to find missing side lengths, and shows how to determine the ratio of perimeters from scale factors. The tutorial concludes with a practical example of framing a poster, applying the learned concepts to find the required amount of framing material.

What is a proportion in the context of ratios?

• An equation that equates two equal ratios

• An equation that equates two unequal ratios

• A formula to calculate volume

• A method to calculate area

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CCSS.7.RP.A.2A

What is the result of cross multiplying 6 times 15 and 10 times TQ?

• 60 equals 10TQ

• 90 equals 10TQ

• 90 equals TQ

• 60 equals TQ

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CCSS.7.G.A.1

Why is the proportion 11 over 22 and 16 over 8 incorrect?

• It equates two unequal ratios

• It incorrectly places the longer side in the numerator

• It uses incorrect figures

• It is actually correct

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CCSS.8.G.A.3

What is the perimeter of a rectangle with a height of 3 and a base of 4?

• 12 units

• 14 units

• 16 units

• 18 units

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CCSS.4.MD.A.3

How does doubling each side of a rectangle affect its perimeter?

• It quadruples the perimeter

• It doubles the perimeter

• It triples the perimeter

• It does not change the perimeter

What does the ratio of perimeters being the same as the ratio of sides imply in similar figures?

• Perimeters scale with side lengths

• Perimeters are independent of side lengths

• Perimeters change with area

• Perimeters are always equal

What is the scale factor between the sides 18 and 24?

• 4 to 3

• 1 to 2

• 3 to 4

• 2 to 3

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CCSS.7.G.A.1

If the large triangle's perimeter is 70, what is the small triangle's perimeter?

• 52.5 units

• 55 units

• 60 units

• 65 units

What scale factor is used to enlarge a 4 by 6 inch photo to a 30 inch tall poster?

• 1 to 5

• 2 to 15

• 4 to 30

• 3 to 20

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CCSS.7.G.A.1

How much framing material is needed for the poster?

• 200 inches

• 100 inches

• 150 inches

• 250 inches

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CCSS.4.MD.A.2