Warm Up

1. Gretchen is making dinner. She has tofu, chicken and beef for an entrée, and French fries, salad and corn for a side. If Ingrid has 6 drinks to choose from, how many meals can Ingrid create?

2. Tory is starting a business. He is choosing a vice president, marketing director and accountant from a pool of 13 applicants. How many ways could Tory create his executive team?

Answers

1. Gretchen is making dinner. She has tofu, chicken and beef for an entrée, and French fries, salad and corn for a side. If Ingrid has 6 drinks to choose from, how many meals can Ingrid create?

2. Tory is starting a business. He is choosing a vice president, marketing director and accountant from a pool of 13 applicants. How many ways could Tory create his executive team?

54 meals

1716 ways

BASIC PROBABILITY

Probability

iespossibilitall

happenwilleventspecificachance

Some Terms!• Theoretical probability - what should happen• Experimental probability - what actually happens in

real life• Outcome - the result of an experiment• Sample Space - all the possible outcomes of an

experiment• Trial - one iteration of an experiment• Event - a specific outcome

Experiment: Rolling a dieOutcomes: 1, 2, 3, 4, 5, and 6Sample space: S = {1, 2, 3, 4, 5, 6}

Example 1

Consider this dartboard. Assume that the experiment is throwing a dart once and that the dart always hits the board. Find:a) The outcomesb) The sample space

Example 2If an experiment consists of tossing a coin three times and recording the results in order, find the sample space. (Find all possible outcomes).

S = {HHH, HHT, HTH, HTT, THH, THT, TTH, TTT}

The event E, showing exactly two heads, consists of all outcomes with two heads. Write the sample space of E.

E = {HHT, HTH, THH}

Example 2 Continued

What is the event F of showing at least two heads?

F = {HHH, HHT, HTH, THH}

What is the event G of showing no heads?

G = {TTT}

Example 2 Continued

• If you flip a coin, what is the theoretical probability that it lands with heads up?

• If you flip a coin, what is the theoretical probability that it lands with tails up?

• How would you find experimental probability?

Example 3

• If you roll a standard die, what is the theoretical probability that it lands with the 3 facing up?

• If you roll a standard die, what is the theoretical probability that it lands with the 3 or the 4 facing up?

Example 4

Suppose we select, without looking, one marble from a bag containing 4 red and 9 purple marbles. What is the probability of selecting a red marble?

Example 5

Example 6What is the probability of getting a sum of 5

when you roll a pair of dice? (Hint: make a chart!)

Rolling a Pair of Dice

Example 7: Your Turn!• What is the probability of choosing, at random, the

ace of spades from a deck of 52 cards?• What is the probability of choosing any ace from a

deck of 52 cards?• What is the probability of drawing a red card from a

deck of 52 cards?• What is the probability of drawing a club from a

deck of 52 cards?

Probability of Multiple Events

So far, we’ve been considering one event at a time. Now, we are going to consider the probability of multiple events.

Example 8A five-card poker hand is drawn from a standard deck

of 52 cards. What is the probability that all five cards are spades?

How many events are there?

Probability of Multiple Events

To find the probability of multiple events, use:

THE FUNDAMENTAL COUNTING PRINCIPLE!

Probability of the first

event

Keep doing this for all the events that occur

Probability of the

second event

Probability of the

third event

Example 9A bag contains 20 tennis balls, four of which are

defective. If two balls are selected at random from the bag, what is the probability that both are defective?