4. +1 polnts My Notes AskYour Computer keyboard failures can be attributed to cl

Question

4. +1 polnts My Notes AskYour Computer keyboard failures can be attributed to clectrical defects or mechanical defects. A repair faciity currenty has 25 failed keyboards, 7 ot which have clectrical detects and 18 of which have mechanical detects. (a) How many ways are there to randomly select 5 of these keyboards for a thorough nspection (without regard to order)? ways (b n how many ways can a sample of 5 keyboards be selected so that exactly two have an electrical defect? ways (c If ? sample of 5 keyboards s randomly selected, what is the probability that at least 4 of these will have a mechanical defect? Round your answer to four dec malp aces

Explanation / Answer

a) Number of ways to select 5 keyboards = 25C5 = 25! / (5! * (25-5)!) = 53130

b) Number of way to select 5 keyboards with 2 electrical defect = 7C2 * 18C3 = 21 * 816 = 17136

c) P(at least 4 will have mechanical defect) = P(4 mechanical defect and 1 electrical defect) + P(5 mechanical defect)

                                                                      = 18C4 * 7C1 / 25C5 + 18C5 / 25C5

                                                                      = 0.5644

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