document.write( "Question 1199989: A box contains N white and M black balls. Balls are randomly selected one at
\n" ); document.write( "a time, until a black one is obtained. If we assume that each selected ball is
\n" ); document.write( "replaced before the next one is drawn, What is the probability that
\n" ); document.write( "a) Exactly n draws are needed.
\n" ); document.write( "b) At least K draws are needed. \n" ); document.write( "

Algebra.Com's Answer #833981 by ikleyn(52781) $\"\"$ $\"About$

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\n" ); document.write( "A box contains N white and M black balls. Balls are randomly selected one at
\n" ); document.write( "a time, until a black one is obtained. If we assume that each selected ball is
\n" ); document.write( "replaced before the next one is drawn, What is the probability that
\n" ); document.write( "a) Exactly n draws are needed.
\n" ); document.write( "b) At least K draws are needed.
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\n" ); document.write( "\n" ); document.write( " In this my post, I will solve part (a), ONLY.\r
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document.write( "Event in part (a) is the intersection of two indepedent events E and F.\r\n" );
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document.write( "    Event E is that first (n-1) draws are white balls.\r\n" );
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document.write( "    Event F is that the n-th draw is a black ball.\r\n" );
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document.write( "Therefore, the probability of event in part (a) is\r\n" );
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document.write( "    P(event in part (a) ) = .    ANSWER\r\n" );
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\n" ); document.write( "\n" ); document.write( "Solved.\r
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