Question

an engineer planning to design a bridge to cross a river is estimating the height of the tower on the old bridge. a picture is shown below. the engineer measures her shadow to be 76.8 inches long, and she knows that she is 64 inches tall. if the length of the shadow of the bridges tower is 216 feet long, what is the approximate height of the tower on the old bridge? a. 150 feet b. 180 feet c. 216 feet d. 12 feet

Explanation:

Step1: Set up proportion

$\frac{64}{76.8}=\frac{x}{216\times12}$ (Convert 216 ft to inches)

Step2: Cross - multiply and solve

$76.8x = 64\times216\times12$
$x=\frac{64\times216\times12}{76.8}=2160$ inches. Convert back to feet: $\frac{2160}{12}=180$ feet

Answer:

b. 180 feet