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probability with raffle tickets

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probability with raffle tickets

by joannabanana » Mon Oct 11, 2010 4:03 am
An a small raffle, there are only 2 prizes, and 30 tickets are sold. A boy has 3 tickets in the raffle. Find the probability that he wins (a) first prize, (b) both prize, (c) only the 2nd prize, and (d) a prize.

[spoiler](a) 1/10 (b) 1/145 (c) 27/290 (d) 28/145. [/spoiler]
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by kmittal82 » Mon Oct 11, 2010 4:31 am
P (first prize) = 3/30 = 1/10

P (first and second prize ) = 3/30 x 2/29 = 1/10 x 2/29 = 2/290 = 1/145

P (second prize) = 27/30 x 3/29 = 27/290

P (first or second prize ) = 1/10 + 27/290 = (29+27)/290 = 56/290 = 28/145
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