Section 7.2

Mutually Exclusive: pulling a jack or queen card from the deck

P(a U b) = P(a) + P(b)

In general,

Reminder U means unionmeans intersection

If two fair dice are tossed, what is the probability that the sum is a 2 or a 3?

Mutually Exclusive!P(a or b) = P(a) + P(b)

= 1/36 + 2/36 = 3/36 = 1/12

13 of the 50 states include territory that lies west of the continental divide. 42 states include territory that lies east of the continental divide. Is this possible? Explain your answer.

Sure, as long as 5 states include territory that lies both east and west of the continental divide (Mt, Wy, Co, NM, Al)

Three fair coins are tossed. What is the probability that NOT all the coins show the same face?

The sample space is 8P(1 heads) + P(2 heads)3/8 + 3/86/8 = ¾ = 75%

Use complementary events to answer the previous question.

1 - P(3 heads) - P(3 tails)1 – 1/8 – 1/81 – 1/4 = ¾ = 75%

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