a) an urn contains four black and five white balls. A ball is drawn at random an

Question

a) an urn contains four black and five white balls. A ball is drawn at random and then replaced, after which a second ball is drawn. Find the proability that the first is black and the second is white.

b) If a pair of fair dice is rolled, what is the proability that the sume shown is either exactly 9 or less than 4 ?

c) A coin is tossed, then a card is drawn from an ordinary deck of 52 cards, and then a die is rolled. What is the probability of obtaining a head on the coin, an ace from the deck and a 5 on the die?

d) If one letter is chose at random from the word boot and one letter from the word toot, what is the probability that both letters match?

Explanation / Answer

1)20/81 1st does not affect 2nd

2)7/36 four ways go get 9 (5&4, 4&5, 6&3, 3&6) and the 3 ways to get less than 4 (1&1, 1&2, 2&1)

3)1/2 * 4/52 * 1/6 = 1/156independent events)

4)3/8 16 total combinations, and 6 of them match, 4 with O's, and 2 with T's.

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