The math class were asked to calculate the distance between two cities that appeared on a map that the teacher handed out. The class measured the distance on the map and found it to be 3 inches. The scale used to draw the map said that ½ inch = 20 miles. Based on this information, what was the approximate distance that the class calculated between the two cities?
a. 110 miles
b. 115 miles
c. 120 miles
d. 125 miles
Answer: c.
Explanation:
In order to calculate the distance the students can set up a proportion as follows to determine what the approximate distance is:
0.5 inches = 20 miles
3 inches = d miles
d = [3 inches x 20 miles] / 0.5 inches
d = [60 inches miles] / 0.5 inches
d = 120 miles
Note that the unites for inches cancel out when the calculation is carried out and we are left with just miles which is what is needed.
©Copyright 2007.Najwa S. Hirn. All rights reserved
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