The speed of your automobile has a huge effect on fuel consumption. Traveling at

Question

The speed of your automobile has a huge effect on fuel consumption. Traveling at 65 miles per hour (mph) instead of 55 mph can consume almost 20% more fuel. As a general rule, for every mile per hour over 55, you lose 2% in fuel economy. For example, if your automobile gets 30 miles per gallon at 55 mph, the fuel consumption is 21 miles per gallon at 70 mph.

If you take a

400 -mile trip and your average speed is

84 mph rather than the posted speed limit of

74 mph, what is the extra cost of fuel if gasoline costs

$2.91 per gallon? Your car gets 29 miles per gallon (mpg) at 64 mph.

Explanation / Answer

total length of trip :- 400 miles

now, car fuel consumption is 29 miles per gallon at 64 miles per hour

cost of fuel (gasoline) :- $2.91 per gallon

now, as the question suggests, we lose 2% fuel economy for every mile per hour over 64mph

so total fuel economy lost is 40% from 29mpg when our average speed of trip is 84mph which is equal to 17.4mpg

and total fuel economy lost is 20% from 29mpg when our average speed of trip is posted speed limit of 74mph, which is equal to 23.2mpg

so, we get that we made a 400 mile trip with average speed of 84 mph and fuel economy was 17.4mpg

and if we made a 400 mile trip with posted average speed of 74 mph the fuel economy would be 23.2mpg

now fuel consumed in first case :- 22.9885 gallons

and fuel consumed in second case :-17.24138 gallons

now extra fuel consumed :- 5.74712 gallons

and extra fuel cost is :-  5.74712 * $2.91 = $16.7241192

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