An urn contains 8 white 5 red and 3 blue chips A person sele

An urn contains 8 white, 5 red and 3 blue chips. A person selects 4 chips without replacement. Determine the following probabilities: (Leave answers in fraction form and do not multiply out any fractions.)

a. Probability that Exactly 2 chips are white

b. Probability the third chip is red

Solution

a)

There are 16C4 = 1820 ways to choose 4 chips.

There are (8C2)(5C2) = 280 ways to choose 2 white and 2 not white chips.

Thus,

P(2 are white) = 280/1820 = 0.153846154 [ANSWER]

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B)

P(third is red) = P(red, red, red) + P(red,not red, red) + P(not red, red, red) + P(not red, not red, red)

= (5/16)(4/15)(3/14) + (5/16)(11/15)(4/14) + (11/16)(5/15)(4/14) + (11/16)(10/15)(5/14)

= 5/16 [ANSWER]