Answer:
80 miles
Step-by-step explanation:
The map scale compares the distance between two points on the map with the corresponding distance on the ground.
That is,
[tex]\boxed{\mathfrak{map\:scale=\frac{distance\:on\:map}{distance\:on\:ground} }}[/tex]
The formula makes it pretty easy to solve!
- map scale is 1 inch : 20 miles
- distance on map is 4 inches
- Let's say, the corresponding distance on the ground is x miles.
Substituting these values in the above mentioned formula:
[tex]\implies \mathsf{\frac{1 \:inch}{20\:miles} =\frac{4\:inches}{x\:miles} }[/tex]
cross multiplying:
[tex]\implies\mathsf{x=4 \times 20}[/tex]
[tex]\implies \mathsf{x=80}[/tex]
That makes the actual distance 80 miles!
ALTER
You can also use simple unitary method here:
1 inch on the map = 20 miles on the ground
∴ 4 inches on the map = 4 × 20 miles on the ground
= 80 miles on the ground
