Building is 10 centimeters tall, actual building is 3 meters tall,

What was the scale used?

1:30

Step-by-step explanation:

A building is 10cm tall.

Actual building is 3m tall.

1m = 100cm

3m = How many cm?

Cross multiplying gives:

3 * 100 = 300cm

The scale used here is:

10 cm represents 300cm

or

10:300

Simplifying gives a scale;

1:30

Meaning that 1cm represents 30cm of the actual building.