Calculating Perimeter from Scale Drawings using Ratios and Proportions

This video tutorial teaches how to compute the actual perimeter from a scale drawing using ratios and proportions. It explains the concept of proportions, demonstrates how to find missing side lengths through cross-multiplying, and highlights common mistakes in setting up proportions. The tutorial also covers calculating the ratio of perimeters using scale factors and applies these concepts to practical scenarios, such as framing a poster. By the end, viewers will understand how to use ratios and proportions to solve real-world problems involving perimeter calculations.

What is a proportion in mathematical terms?

• An equation that relates two unequal ratios

• A method to find the area of a shape

• A technique to measure angles

• An equation that relates two equal ratios

How can you find the length of a missing side using proportions?

• By cross-multiplying the ratios

• By adding the lengths of all sides

• By dividing the perimeter by the number of sides

• By subtracting the smaller side from the larger side

What is a common mistake when setting up proportions?

• Calculating the area instead of the perimeter

• Placing the longer side in the numerator of one ratio and in the denominator of another

• Ignoring the units of measurement

• Using the same number for both ratios

How is the ratio of perimeters related to the ratio of sides in similar figures?

• The ratio of perimeters is unrelated to the ratio of sides

• The ratio of perimeters is the same as the ratio of sides

• The ratio of perimeters is always twice the ratio of sides

• The ratio of perimeters is half the ratio of sides

If a rectangle's sides are doubled, what happens to its perimeter?

• The perimeter remains the same

• The perimeter is doubled

• The perimeter is halved

• The perimeter is tripled

What is the scale factor if a 4-inch height is scaled to a 30-inch height?

• 1 to 5

• 4 to 30

• 3 to 10

• 2 to 15

How much framing material is needed for a poster with a perimeter ratio of 2 to 15 and a small perimeter of 20 inches?

• 100 inches

• 250 inches

• 200 inches

• 150 inches