5.5 Examples
1. How many ways can 15 students be lined up.
2. Outside a home there is a keypad that will open the garage if the correct four-digit code is entered.
a. How many codes are possible?
b. What is the probability of entering the correct code on the first try, assuming that the owner does not
remember the code?
3. A lottery exists where balls numbered 1 to 25 are placed in an urn. To win, you must match the four balls chosen
in the correct order. How many possible outcomes are there for this game?
4. Suppose that there are 55 Democrats and 45 republicans in the U.S. Senate. A committee of seven senators is to
be formed by selecting members of the Senate randomly.
a. What is the probability that the committee is comprised of all democrats?
b. What is the probability that the committee is comprised of all republicans?
c. What is the probability that the committee is comprised of three democrats and four republicans?