Calculating Actual Lengths from Scale Drawings Using Ratios and Proportions

This video tutorial teaches how to calculate actual lengths from scale drawings using ratios and proportions. It explains the concepts of ratios and proportions with examples, including common mistakes. The tutorial covers solving proportions by equating ratios and using cross multiplication, demonstrating these methods with similar triangles and parallelograms. The video concludes with an application of these concepts to create a scale model of the Parthenon, emphasizing the use of cross multiplication for accurate calculations.

What is a ratio?

• A type of geometric shape

• A method to solve equations

• An equation that relates two equal ratios

• A comparison between two numbers

Which of the following is a correct proportion?

• 3/4 = 6/8

• 5/6 = 10/12

• 7/8 = 14/15

• 2/3 = 4/5

How do you solve a proportion by equating ratios?

• By adding the numerators

• By equating the cross products

• By dividing the denominators

• By subtracting the means

What is the purpose of cross-multiplying in solving proportions?

• To simplify the equation

• To find the mean of the numbers

• To add the numerators and denominators

• To equate the products of the extremes and means

Why is cross-multiplying useful?

• It eliminates the need for division

• It works only with round numbers

• It simplifies complex equations

• It is effective even with non-round numbers

In the scale model problem, what does 1 inch represent?

• 10 actual feet

• 15 actual feet

• 20 actual feet

• 25 actual feet

How long should the scale model be if the actual length is 225 feet?

• 12 inches

• 10 inches

• 18 inches

• 15 inches