Final answer:
To solve the equation 21 × x = 9.4, divide both sides by 21 to find x ≈ 0.45. For the proportion 1.5 inches/10 feet = 42 inches/x feet, cross-multiplying and solving for x gives the building's height as 280 feet.
Step-by-step explanation:
The model below represents an equation: 21 × x = 9.4. What value of x makes the equation true? To find x, we can divide both sides of the equation by 21, which gives us x = 9.4 / 21. Performing the division, we get x = 0.447619. However, normally we would round the result to a reasonable number of significant figures, especially in the context of a middle school math problem. Therefore, to two significant figures, x ≈ 0.45.
To solve the equation 1.5 inches/10 feet = 42 inches/x feet, we can set up a proportion and cross multiply to find the actual height of the building. Cross multiplication gives us 1.5x = 420, and by solving for x, we find the height of the building in feet, x = 280 feet.