Final answer:
The question is about calculating fuel efficiency in miles per gallon, which is a mathematical ratio. By dividing the miles driven by the gallons used, one can determine a vehicle's fuel economy and compare it to national averages or to the fuel efficiency required to be more eco-friendly than flying.
Step-by-step explanation:
The question pertains to determining the fuel efficiency of vehicles, which is a matter of dividing the number of miles traveled by the number of gallons of gas used. This is an application of ratio and proportion, which is a topic covered within mathematics. Example 20.3.12 provides details of two vehicles' mileage and gasoline usage which can be used to calculate their respective miles per gallon (MPG) and then determine the daily average use per person. With this data, one can compare personal fuel economy to the national average.
For instance, to find the efficiency of one of the vehicles in the given example, which drove 400 miles using 22 gallons of gasoline, divide 400 miles by 22 gallons, resulting in approximately 18.18 MPG. Similarly, the other vehicle covered 8,660 miles with 69 gallons, resulting in about 125.51 MPG.
To calculate the daily average use per person, one would need to know the number of people in the household, which is not provided in the example. However, if that information were available, you would divide the total number of miles driven by the household by the total gallons used by all vehicles and then divide that number by the number of days in the year and the number of people in the household.
Comparisons to the national average, which suggest a fuel economy about 30 times lower than the MPG of typical cars, provide a context for the importance of tracking one's fuel use.
Considering the CO₂ emissions related to fossil fuel use, a decision to drive or fly can be made by comparing the fuel efficiency of a car to that of a fully-occupied airplane. If, for example, a car's MPG exceeds that of an airplane's MPG per passenger, driving would be the more fuel-efficient choice. In terms of fuel economy and efficiency, it can be challenging to find cars with performance as good as the 90 MPG per passenger that a fully occupied airplane might offer.
When it comes to fuel economy's environmental impact, always remember that variations such as temperature can affect how far you can drive on a given amount of gas. As demonstrated in Figure 13.13, gas expands with increasing temperature, which means a car might not drive as far on 'empty' during summer than in winter.