Probability

H

This key displays two menus: PRB and RAND.

PRB contains the following options:

nPr

Calculates the number of possible permutations of n items taken r at a time, given n and r. The order of objects is important, as in a race.

nCr

Calculates the number of possible combinations of n items taken r at a time, given n and r. The order of objects is not important, as in a hand of cards.

!

A factorial is the product of the positive integers from 1 to n. n must be a positive whole number { 69.

RAND contains the following options:

rand

Generates a random real number between 0 and 1. To control a sequence of random numbers, store an integer (seed value) | 0 to rand. The seed value changes randomly every time a random number is generated.

randint(

Generates a random integer between 2 integers, A and B, where A { randint { B. Separate the 2 integers with a comma.

Examples

nPr

8

 

H 1

 

3 <

nCr

52 H 2

5 <

!

4 H

3 <

STO 4 rand

5 L H "

 

1 <

Rand

H " 1 <

Randint(

H " 2

3 % ` 5 E <

³ Problem

An ice cream store advertises that it makes 25 flavors of home made ice cream. You like to order three different flavors in a dish. How many combinations of ice cream can you test over a very hot summer?

25

H 2

3 <

You can choose from 2300 dishes with different combinations of flavors! If a long hot summer is about 90 days long, you will need to eat about 25 ice cream dishes each day!