The mean gas mileage for a hybrid car is 57 miles per gallon. Suppose that the gasoline mileage is approximately normally distributed with a standard deviation of 3.5 miles per gallon. What proportion?

To find the proportion of hybrid cars that achieve a certain gas mileage, we would use the properties of the normal distribution. For example, if we want to determine the proportion of cars that get more than 60 miles per gallon, we would calculate the z-score: ( z = \frac{(60 - 57)}{3.5} \approx 0.86 ). Using a standard normal distribution table or calculator, we find that the area to the right of this z-score corresponds to the proportion of cars achieving that mileage. The exact proportion can be determined based on the z-score calculated.