Chapter 6, Problem 8PS

Toby’s Trucking Company determined that the distance travelled per truck per year is normally distributed, with a mean of 50 thousand miles and a standard deviation of 12 thousand miles.

a. What proportion of trucks can be expected to travel between 34 and 50 thousand miles in a year?

b. What percentage of trucks can be expected to travel either less than 30 or more than 60 thousand miles in a year?

c. How many miles will be travelled by at least 80 percent of the trucks?

d. What are your answer to $\left(\text{a}\right)\text{through}\left(\text{c}\right)$ if the standard deviation is 10 thousand miles?