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When going more than 38 miles per hour, the gas mileage of a certain car fits the model 4072-01-02-03-00_files/i0120000.jpg where x is the speed of the car in miles per hour and y is the miles per gallon of gasoline. Based on this model, at what speed will the car average 15 miles per gallon?  (Round to nearest whole number.)
 Jan 9, 2015

Best Answer 

 #1
avatar+128475 
+5

y = 43.81 - .395x    let y = 15....so we have

15 = 43.81 - .395x   subtract 43.81 from both sides

-58.81 = -.395x       divide both sides by -.395

x = about 149 mph  !!!!

 

 Jan 9, 2015
 #1
avatar+128475 
+5
Best Answer

y = 43.81 - .395x    let y = 15....so we have

15 = 43.81 - .395x   subtract 43.81 from both sides

-58.81 = -.395x       divide both sides by -.395

x = about 149 mph  !!!!

 

CPhill Jan 9, 2015

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