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Miles per Gallon

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Miles per Gallon

by LSB » Tue Aug 19, 2008 3:15 pm
A car averages 25 miles per gallon in the city and 40 miles per gallon on the highway. According to these rates, which of the following is closest to the number of miles per gallon that the car averages when it is driven 10 miles in the city and 50 miles on the highway

A 28
B 30
C 33
D 36
E 38

When do you use weighted averages (i.e. 1/6 * 25 + 5/6 *40) vs calculating totals and averaging the total?

OA D
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by klamation » Tue Aug 19, 2008 6:08 pm
10 miles / 25 miles per gallon = .40 gallons
50 miles / 40 miles per gallon = 1.25 gallons

Total gallons used = .40 + 1.25 = 1.65
Total miles driven = 10 + 50 = 60

Miles per gallon = 60 / 1.65 = 36.3 which is closest to D
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