In how many ways can six books be arranged on a shelf?

A jar contains nine balls numbered 1 through 9. A single ball is selected at random three times. How many three-digit numbers can be formed if the selections are made with replacement?

A jar contains five balls individually numbered 3 through 7. A single ball is selected at random four times. How many four-digit numbers can be formed if the selections are made without replacement?

The password to log onto a computer consists of a five character entry code. The first three characters use the letters a through z, and the last two characters use the digits 0 through 9. How many five character entry codes are possible if repetition is not allowed?

A sock drawer contains 6 black, 5 white, 4 brown, 5 blue, 1 green, 3 stripped, and 2 plaid socks. What is the fewest number of selections that must be made to ensure you would have 2 socks that are the same?