Question

12​-foot wall measures 2.5 inches on a scale drawing. In the​ drawing, a second wall is 9 inches long. What is the actual length of the second​ wall?

Answer 1

43.2 ft

Explanation:

Scale problems usually can be solved with proportions.

The wall whose real and scale drawing lengths you know gives you a ratio of real to scale drawing.

The ratio of real size to drawing size is:

12 ft to 2.5 in.

The drawing size of the second wall is 9 in.

We are looking for the real size of the 9-inch wall.

Let the unknown length be x.

For the 9-inch wall, the ratio of real to drawing size is

x to 9 in.

Now we set the two ratios equal. That is called a proportion.

12 ft to 2.5 in. = x to 9 in.

Use fractions for the ratios.

`(12~ft)/(2.5~in.) = (x)/(9~in.)`

To solve the proportion, we cross multiply.

`2.5x = 9 * 12`

2.5x = 108

x = 108/2.5 = 43.2

Answer: 43.2 ft