91Ó°ÊÓ

The number of miles driven by a truck driver falls between $300\mathrm{and}700$, and follows a uniform distribution.

a. Find the probability that the truck driver goes more than $650$miles in a day.

b. Find the probability that the truck drivers goes between $400\mathrm{and}650$miles in a day.

c. At least how many miles does the truck driver travel on the furthest $10\%$of days?

Suppose that the length of long distance phone calls, measured in minutes, is known to have an exponential distribution with the average length of a call equal to eight minutes.

a. Define the random variable.$X$= ________________.

b. Is $X$continuous or discrete?

c.$X~$ ________

d.$\mathrm{μ}=$ ________

e.$\mathrm{σ}=$________

f. Draw a graph of the probability distribution. Label the axes.

g. Find the probability that a phone call lasts less than nine minutes.

h. Find the probability that a phone call lasts more than nine minutes.

i. Find the probability that a phone call lasts between seven and nine minutes.

j. If $25$phone calls are made one after another, on average, what would you expect the total to be? Why?