Unit 5 – Rates, Ratios, and Proportions
Lesson 4 – Proportions and Scale
Blue Handout
Blue – Proportions and Scale
1. The scale on a map is 1/8 inch = 260 miles. How far apart are two cities that are
1
1 inches apart on the map?
16
2. The scale on a globe is 1/8 inch equals 125 miles. How many inches is the
circumference of that globe? (Use 25,000 miles for the circumference of the
earth.)
Solutions
1. 2210 miles
1
1
1
inch
16
8
=
Set up a proportion:
260 miles
n miles
Cross-multiply:
1
n=
inch
17 •260
8
16
Divide both sides by 1/8 (which is the same as multiplying by 8/1): n = 2210 miles
2. 25 inches
1
inch ( globe )
n ( globe circumference )
8
Set up a proportion:
=
125 miles (real ) 25, 000 miles (real circumference )
Cross-multiply: 125n = 3125
Divide both sides by 125: n = 25 inches
1
Unit 5 – Rates, Ratios, and Proportions
Lesson 4 – Proportions and Scale
Blue Handout
Bibliography Information
Teachers attempted to cite the sources for the problems included in this problem set. In some cases,
sources may not have been known.
Problems
Bibliography Information
1-2
Zaccaro, Edward. Challenge Math (Second
Edition): Hickory Grove Press, 2005.
2