Probability

November 13, 2014

SAT Fill-In Question

•How many positive factors does the number 120 have?

•120 = 2·2·2·3·5 = 23·31·51 •A factor must have 2s and/or

3s and/or 5s, so let’s draw blanks.

One-Minute Question

•How many positive factors does the number 120 have?

•120 = 2·2·2·3·5 = 23·31·51

For 2s For 3s For 5s

4 2 2= 16

What’s the probability?

•How many people are in this class?

• If I choose one of you randomly to answer the next question, what’s the probability that I choose you?

What’s the probability?

that if I toss 3 coins, exactly one of them will land “heads up”?

What’s the probability?

•That if we roll 2 dice, the sum of the dice will be greater than 6?

Probability

•A trial is a systematic opportunity for an event to occur.

•An experiment is one or more

trials.

Probability

•The Sample Space is the set of all possible outcomes of an event.

Probability

•The probability of an event E, which is a subset of a finite sample space S of equally likely outcomes, is p(E) = .

E

S

Probability

•In simpler terms, probability is the number of ways you get what you want, divided by the number of ways events could happen.

A candy jar contains 6 peppermint, 4 spearmint, 3

butterscotch and 2 cinnamon candies.

• If I select one of these candies at random, what is the probability that I get a spearmint?

• N(Sample Space) = 15 candies• N(Success) = 4• Probability = 4/15

A candy jar contains 2 spearmint and 2 cinnamon

candies.• If I select two of these candies at random,

what is the probability that I get both spearmints?

• Sample Space = {S1S2, S1C1, S1C2, S2C1, S2C2 C1 C2 }

• N(Success) = 1 (The SS)• Probability = 1/6

If I toss a dart at the target below, what is the

probability that I get 20 points?

10

20

30

Radii are 2 inches, 6 inches and 10 inches.