Set up a proportion using the given scale.

Here are the solutions to your questions:

2.1 A particular map shows a scale of $1 \text{ cm} : 10 \text{ km}$. What would the map distance (in cm) be if the actual distance is $20 \text{ km}$?

Step 1: Set up a proportion using the given scale.

$$\frac{1 \text{ cm}}{10 \text{ km}} = \frac{\text{Map distance}}{20 \text{ km}}$$

Step 2: Solve for the map distance.

$$\text{Map distance} = \frac{1 \text{ cm} \times 20 \text{ km}}{10 \text{ km}}$$ $$$$