Scale Drawings
(Teacher Copy)
Activity 9: Road and City Maps
Students use state and city maps as scale drawings to estimate distances. Also use page S9.
To understand how ratios are used in scale drawings.
Introduction:
Have you ever wanted to take a trip? Find lost treasure?
Rearrange your room? Build a scale model of a car, airplane, or space
ship? All of these activities can involve the use of scale drawings.
Have students locate the legend on each map and determine the scale.
Part A
Sample answers are based on a 1993 AAA Indiana road map.
5 miles » 0.385 inches
1 inches = 13 miles
Scottsburg to Memphis » 1 1/8
(1.125) inches
Scottsburg to Memphis » 14.6
miles
Perimeter of BedfordUniontownHenryvillePaoli rectangle »
9 inches direct distance (answers will vary if distances are determined
by following various roadways, but they should be equal to or greater than
the directdistance figure)
Bedford to Uniontown » 36.5 miles
Entire trip » 117 miles direct
distance (estimates and actual distances will vary according to the roadways
followed, although these distances should exceed the directdistance figure)
Part B
Answers will vary.
Closing Discussion
Why are map scales ratios? Would it be possible to provide a
table instead of the map scale? What would such a table look like?
Map scales are ratios because distance is a ratio of inches to miles.
It would be possible to provide a table on a map instead of a scale (a
table is provided on some maps), but a scale is always provided because
it is a single, simple ratio that applies to the entire scale drawing.
A table on a map that did not also have a scale would have to have a row
for distance in inches and a row for distance in miles; some city names
might be included in the table.
When you read the mileage table on a road map, the distance shown between
cities is often a little different from the distance you get by measuring.
Why is this the case? The distance shown on maps is based on the
route most likely to be traveled, but only an approximate measure can be
made using a ruler (which is straight).
All of the scales we have used in this lesson are ratios that have
different units. Is it possible to have a map drawn using a
sameunits ratio? Explain. It would be possible but impractical
to have a map drawn using a sameunits ratio. For example, a 5milesperinch
scale is also a 316,800inchto1inch scale, and people are interested
in distances between cities in miles, not inches.
Further Exploration
Find a blueprint of a house or small building. Discuss the scale
used and exactly how large a building constructed from your blueprint would
be. Using tape, outline the actual size of one of the rooms on your
classroom floor.
© Copyright
Area 10 Mathematics and Technology Professional Development Center
Permission is granted to duplicate these materials for classroom use.
Last updated on 1/30/1999
Comments: egalindo@indiana.edu
http://www.indiana.edu/~atmat/units/ratio/ratio_t4.htm
