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awesome problem.

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by rros0770 » Thu Sep 23, 2010 8:56 am
Is choice B (1/21) the OA or is that answer incorrect? I'm coming up with[spoiler] D (37/42)[/spoiler]
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by goyalsau » Thu Sep 23, 2010 9:57 am
You are absolutely Right but once again .
HOW??????????
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by Ian Stewart » Thu Sep 23, 2010 10:00 am
That question is absurdly long; most of the information is irrelevant (and the question omits the very relevant information that the jars are picked at random). Where is the question from? For our paint to be one of the two types of 'jaune' we need to use at least one jar of yellow paint. The probability we do not choose any yellow jar is (5/9)(4/8)(3/7), so the probability we do use at least one yellow jar is 1 - (5/9)(4/8)(3/7) = 37/42.

This is really just a variation on the typical marbles problem; it's just asking "If you have 4 yellow marbles and 5 non-yellow marbles in a bag, and you pick three at random and without replacement, what is the probability you pick at least one yellow marble?"

If the question asked about 'Jaune X' or 'Jaune Y' paint, it would then be a bit more interesting, but it would still be a standard variation on the typical marbles setup.
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