Question

When going more than 38 miles per hour, the gas mileage of a certain car fits the model y=43.81-0.396x 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.)

a. 149
b. 98
c. 48
d. 73

Answer 1

d. 73

The car will average 15 miles per gallon at the speed 73 miles per hour

Explanation:

Your equation is: y = 43.81 - 0.395x

We need to solve for x if y = 15

So plug 15 into your equation: 15 = 43.81 - 0.395x

Then rearrange your equation to get the variable by itself and change the sign: 0.395x = 43.81 - 15

Subtract 43.81 - 15 = 28.81

0.395x = 28.81

Then divide both sides of the equation by 0.395

0.395x/0.395 = 28.81/0.395

x = 72.9367088608

Then (Round to nearest whole number.)

Giving you your solution of 73

To Conclude:

The car will average 15 miles per gallon at the speed 73 miles per hour .

Answer 2

I set the equation equal to 15 and got that the answer was d.73