The mean life of a Brand Q car battery is 36 months. The standard deviation is 4 months. 68% of all batteries will have a life between months and months.

68% of all batteries will have a life between 32 months and 40 months.

Step-by-step explanation:

The Empirical Rule states that, for a normally distributed random variable:

68% of the measures are within 1 standard deviation of the mean.

95% of the measures are within 2 standard deviation of the mean.

99.7% of the measures are within 3 standard deviations of the mean.

In this problem, we have that:

Mean = 36.

Standard deviation = 4.

68% within 1 standard deviation of the mean.

36 - 4 = 32

36 + 4 = 40

68% of all batteries will have a life between 32 months and 40 months.