Question

Carole's car averages 13.2 mi/gal in city driving and 25.3 mi/gal in highway driving. If she drove a total of 396.0 mi on 19 gal of gas, how many of the gallons (to the nearest gallon) were used for city driving?

Answer 1

Answer:

7 gallons were used for city driving.

Step-by-step explanation:

I am going to solve this question by a system of equations.

I am going to say that:

x is the number of gallons driven in the city.

y is the number of gallons driven in the highway.

19 gal of gas

This means that $x + y = 19$

Carole's car averages 13.2 mi/gal in city driving and 25.3 mi/gal in highway driving. If she drove a total of 396.0 mi.

This means that $13.2x + 25.3y = 396$

How many of the gallons (to the nearest gallon) were used for city driving?

This is x

From the first equation, i will have

$y = 19 - x$

Replacing in the second equation

$13.2x + 25.3y = 396$

$13.2x + 25.3(19 - x) = 396$

$13.2x - 25.3x = 396 - 480,7$

$12.1x = 84.7$

$x = \frac{84.7}{12.1}$

$x = 7$

7 gallons were used for city driving.