Question 135285
testers drive 8 cars 200 miles on a test track at the same speed 
1.20gal 2.18 gal 3. 16 gal 4. 12 gal 5. 10 gal 6. 12 gal 7. 7 gal 8. 5 gal 
a. find the fuel efficiency in mile per gal per car?
Divide 200 miles by each gallon number to get miles per gallon.
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c. Write a formula for calculating the fuel efficiency based on fuel used for a 200 mile test.
fuel efficiency = 200 mile/(# of gallons)
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d. tell how fuel efficiency changes as amount of fuel used increases from 5 to 10 gal. from 15 to 20 gal 
fuel efficiency = 200/5 = 40 mpg ; 
fuel efficiency = 200/10 = 20 mpg;
fuel efficiency = 200/20 = 10 mpg;
As the # of gallons used doubles the mpg goes down by 50%
The relation is exponential as mpg is multiplied by 1/2 then 1/2 then 1/2 etc.
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e. how do the answers in (d) show they are not linear
Linear relations show a constant additive; "d" shows a constant multiplier.
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Cheers,
Stan H.