The life expectancy of a certain tire is a normal distribution with the mean = 40,000 miles, standard deviation is 1,000 miles. find the probability that a tire will last more than 39,000 miles.

Step-by-step explanation:

The average is:

The standard deviation is:

We want the probability that a tire lasts more than 39,000 miles.

This is:

Now we must transform these values to those of a standard normal distribution to facilitate calculation by using the probability tables.

This is:

---------- (For the symmetry of the standard normal distribution)

When you search for the normal standard table, you get the following value:

use formula for the circle a=3.14

step-by-step explanation: