Question

The door on a model building is 10 centimeters tall. The door on the actual building is 3 meters tall.

What was the scale used?

A) 1:30
B) 1:3
C) 10:3
D) 1:300

Answer 1

The answer is A. What you do is you put the numbers given into the ration. You have to convert the meters to centimeters so the ratio will be accurate. After you do that, you reduce. The picture explains better.

Answer 2

First of all, let's translate both measurements to the same units. We'll stick with centimeters to avoid decimal numbers. So, the 10 centimenter on the map are fine, while the actual 3 meters becomes 300 centimeters.

To find the scale, simply consider the ratio between the map and actual measurements: 10 centimeters on the map correspond to 300 actual centimeters, so the ratio is

`\cfrac{\text{map measurement}}{\text{actual measurement}} = \cfrac{10}{300} = \cfrac{1}{30}`