Please help with part D, thanks!
A trucking company determined that the distance traveled per truck per year is normally distributed, with a mean of 30 thousand miles and a standard deviation of 12 thousand miles.
a. What proportion of trucks can be expected to travel between 16 and 30 thousand miles in a year?
The proportion of trucks that can be expected to travel between 16 and 30
thousand miles in a year is 0.3784
b. What percentage of trucks can be expected to travel either less than 20 or more than 50 thousand miles in a year?
The percentage of trucks that can be expected to travel either less than 20
or more than 50 thousand miles in a year is 25.02%
c. How many miles will be traveled by at least 75% of the trucks?
The number of miles that will be traveled by at least 75% of the trucks is 21,906 miles.
d. What are your answers to parts (a) through (c) if the standard deviation is 10 thousand miles?
If the standard deviation is 10 thousand miles, the proportion of trucks that can be expected to travel between 16 and 30 thousand miles in a year is ???