§12.3 Probability

The probability of an event measures the chances of an event occurring.

The probability is always between 0 and 1.

Probability

The probability an event will succeed is

#( )

#

of ways to succeedP success

total of possible outcomes

Probability, not permutation

Example 1:

Suppose you select two letters at random from the word “fragile”. Find each probability.

A) P(2 vowels)

B) P(2 consonants)

C(1 vowel, 1 consonant)

Example #2:There are 10 boys and 12 girls in a class. What is the probability of choosing a group of 5 people with:

A) P(all boys)B) P(2 boys, 3 girls)C) P(all girls)

Example 3:A bag contains 3 red3 red, 4 4 greengreen and 2 blue marbles. If two balls are selected at random, (without (without replacement)replacement) what is the probability of choosing:

a) P(2 red)b) P(1 red and 1 blue)

Example 4:Sam has 4 Jazz CD’s, 3 Rap

CD’s and 1 Classical CD. If she chooses one CD, puts it back and then chooses another CD, What is the probability that she chooses:

a) 1 jazz and 1 jazzb) 1 classical and 1 rap

A deck of Cards Contains:A deck of Cards Contains:

52 Cards

4 suits ♥ ♦ ♠ ♣13 cards of each suitFace cards: Jack, Queen,

King

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