Raffle TicketsDate: 08/20/97 at 07:39:49 From: mostyn Subject: Probability What is the best way to do this: A man buys 5 tickets in a raffle in which 100 tickets are sold. If there are three prizes in the raffle, find the probability that the man: (a) wins exactly one prize; (b) wins at least one prize. I figured it out using a tree diagram, and multiplying probabilities of the branches, but is there a better way? Date: 08/26/97 at 13:31:25 From: Doctor Rob Subject: Re: Probability Let C(a,b) = a!/(b!*(a-b)!). (a) C(3,1)*C(97,4)/C(100,5) is the probability of choosing one out of the three winning tickets and choosing four out of the 97 losing tickets as a favorable result of choosing five out of the 100 tickets sold. (b) This probability is 1 - C(3,0)*C(97,5)/C(100,5), since the last term is the probability of choosing zero out of the three winning tickets and five out of the 97 losing tickets. -Doctor Rob, The Math Forum Check out our web site! http://mathforum.org/dr.math/ |
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