document.write( "Question 1203755: Suppose a jar contains 18 red marbles and 30 blue marbles. If you reach in the jar and pull out 2 marbles at random at the same time, find the probability that both are red.
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Algebra.Com's Answer #839576 by math_helper(2461) $\"\"$ $\"About$

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document.write( "This problem can be thought of as drawing one marble and then a 2nd marble, without replacement:\r
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document.write( "P(first is red) = 18/(18+30) = 18/48
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document.write( "P(2nd is red) = 17/(17+30) = 17/47\r
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document.write( "P(both are red) = (18/48)*(17/47) = 306/2256 or approx. 0.1356 (13.6%)\r
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document.write( "If you compute it assuming both are drawn at the same time, you get:
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document.write( "  C(18,2) / C(48,2) = ((18*17)/2) / ((48*47)/2) = (18*17)/ (48*47) = 306/2256, as above.\r
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document.write( "Where C(n,r) = n!/((n-r)!r!)
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