Answer:
C. 3.6 gallons.
Explanation:
Let
be the raw score corresponding to z-score 0 and
be the raw score corresponding to z-score 3.
We have been given that the number of gallons of gasoline per day used by a car is normally distributed with a mean of 2.2 gallons and a standard deviation of 1.2 gallons.
We will use z-score formula to solve or given problem.
, where,
,
,
,
.
Now we will find raw scores corresponding to given z-scores as:
and

Now we will multiply both sides of our equations by 1.2.
and

and

Now we will add 2.2 to both sides of our equations.
and

and

Now let us find the difference of our both raw scores to find the difference in gallons per day used by both cars.



Therefore, the difference in gallons of gasoline used per day by both cars is 3.6 gallons and option C is the correct choice.