We can calculate combinations, permutations, and factorials with functions COMB, PERM, and ! from the MTH/PROBABILITY.. sub-menu. The operation of those functions is described next:

•COMB(n,r): Calculates the number of combinations of n items taken r at a time

•PERM(n,r): Calculates the number of permutations of n items taken r at a time

•n!: Factorial of a positive integer. For a non-integer, x! returns Γ(x+1), where Γ(x) is the Gamma function (see Chapter 3). The factorial symbol (!) can be entered also as the keystroke combination

~‚2.

Example of applications of these functions are shown next: [Note: not all lines will be visible when done with the exercises in the following figure.]

Random numbers

The calculator provides a random number generator that returns a uniformly distributed random real number between 0 and 1. To generate a random number, use function RAND from the MTH/PROBABILITY sub-menu. The following screen shows a number of random numbers produced using RAND. (Note: The random numbers in your calculator will differ from these).

Additional details on random numbers in the calculator are provided in Chapter 17 of the user's guide. Specifically, the use of function RDZ, to re-

Page 15-2