We use a map to find out how to get from one
place to another. We also use it to estimate what the driving
distance is between point A and point B and plan out the
alternative or shortest route to get there. Maps are often
drawn to a reduced scale such as 1 inch to 20 miles. If they were
drawn to the full scale, you’d have to have a pretty big
piece of paper. For a world map, you would virtually need a sheet
of paper larger than the world itself!
Ratio is the mathematical concept that is used
to develop scaled maps. If mapmakers do not use the concept of
ratio, their maps will not be to scale. As a result, you may
misjudge the actual distance where you want to go.
The equation for finding the distance between
two cities on a map is:
D = d ´
d = distance on map in inches
S = scale (miles/inch)
D = actual distance in miles
From City A to City B, it is 5 inches on the
map. Each inch equals 13 miles. How many miles is the actual
D = d ´ S
D = 5 ´ 13
D = 65
The actual distance is 65 miles.
You are drawing a map of your city for a school
project. The area is 33 miles by 20 miles and you want to show it
on a standard piece of 11"x 8.5" paper. What scale should you draw
the map to?
Estimate the answer:
to 2 miles
to 3 miles
to 5 miles
to 10 miles