5/17 Bell Ringer

You draw one marble from a bag:• What’s the probability you select a blue marble?

• What’s the probability you select a yellow marble?• What’s the probability you select a blue or yellow

marble?• What’s the probability you select a blue and yellow

marble?

Color Green Red Blue Yellow

# marbles 10 10 12 18

Homework: Finish today’s Independent Practice

5/17 News and Notes:

• Perfection: 8th Period

• Quiz Friday• Missing Quizzes – Today after school:

– 2nd: Jahmeelah, Edna, Jairo– 4th: Janet, Monica, Shacora, Jasmine

43 3

5 5

0

2

4

6

1st 2nd 4th 7th 8th

Perfection Competition Daily Results

Quick Definition

• Mutually Exclusive: Two events that cannot both happen.

• Ex: A coin cannot be heads and tails, a ball cannot be blue and yellow.

Example 1

• Melissa has been keeping track of the following two events: She gets a pop quiz in science class with probability 0.12, and she has to dress for PE with probability 0.5.

P(A) = Prob. Of pop quiz = 0.12

P(B) = Prob of dressing in PE = 0.5

Are they M.E.? – NO!

Answer the following questions

• What’s the probability that Melissa has a quiz AND has to dress?

• P(A ∩ B) = P(A)*P(B)

= 0.12 * 0.5

= 0.06

• What’s the probability that she has a quiz OR has to dress?

• P(A U B) = P(A) + P(B) – P(A ∩ B)

= 0.12 + 0.5 – 0.06

= 0.56

Example 2

• 8 cards (2 heart, 2 spade, 2 club, 2 diamond) are laid out on a desk. What’s the probability of drawing a heart or a spade?

• P(A) = Prob. Of drawing a heart

• P(B) = Prob. Of drawing a spade

• Are they M.E.? YES!

• P(Heart) = 2/8 = 0.25

• P(Spade) = 2/8 = 0.25

• P(Hrt U Sp) = P(H) + P(S) – P(H ∩ S)

= 0.25 + 0.25 – 0

= 0.50

What’d you notice?

• P(A U B) = P(A) + P(B) – P(A ∩ B) if not M.E.

• But if M.E. P (A ∩ B) = 0

• So, P(A U B) = P(A) + P(B) if M.E

Guided Practice

• Mr. Chrischilles decided to do his wedding reception at an outdoor Vineyard in Iowa next July. This raised a couple of concerns for his fiancée. She was worried that it might rain, and that it might be too hot (over 80°). To minimize her concerns, Mr. Chrischilles decided to do some key calculations.

Questions on your card.

• The probability that it rains on a given day in July is 0.15 and the probability that it is over 80° is 0.05. Answer the following questions on your card.

• 1. Are the rain and heat mutually exclusive?• 2. What’s the probability that it will be too hot and

rain during the reception?FLIP YOUR CARD• 3. What’s the probability that it will be too hot OR

rain?• 4. What’s the probability that the weather will be

just fine (no rain or not too hot)?

Independent Practice

Exit Ticket

• A classroom has 10 freshmen, 10 sophomores, 15 juniors and 15 seniors. What’s the probability that a randomly selected student is a sophomore or junior?

A. 0.45

B. 0.5

C. 0.25

D. 0.20