Question

An engineer designed a new bridge and drew the scale drawing shown below. 6 Inches If the engineer used the scale 3 inch = 40 feet, how long is the actual bridge the engineer designed?​

Answer 1

If an engineer designed a new bridge and drew the scale drawing shown below. The actual length of the bridge that the engineer designed is 80 feet.

What is the length?

The scale given is 3 inches = 40 feet which implies that every 3 inches on the scale drawing represents 40 feet in reality.

To find the length of the actual bridge set up a proportion using the given scale:

3 inches (scale drawing) corresponds to 40 feet (actual length)

6 inches (scale drawing) corresponds to x feet (actual length of the bridge)

Using the proportion:

3 inches / 40 feet = 6 inches / x feet

Cross-multiply:

3 inches * x feet = 6 inches * 40 feet

Simplify:

3x = 240

Dividing both sides by 3:

x =240/3

x = 80

Therefore the actual length of the bridge that the engineer designed is 80 feet.

Answer 2

The bridge is 80 feet long

Explanation:

We will use the ratio method to solve the question

∵ The engineer used the scale 3 inch = 40 feet

∴ The scale drawing is ⇒ 3 inche : 40 feet

∵ The drawing length of the bridge is 6 inches

→ By using the ratio method

→ inch : feet

→ 3 : 40

→ 6 : x

→ By using cross multiplication

∵ 3 × x = 6 × 40

∴ 3x = 240

→ Divide both sides by 3

∴ x = 80

∵ x represents the actual length of the bridge

∴ The bridge is 80 feet long