document.write( "Question 1188499: Let X represent the difference between the number of heads and the number of tails when a coin is tossed 41 times. Then P(X=11)= \n" ); document.write( "
Algebra.Com's Answer #819606 by ikleyn(52803)\"\" \"About 
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\n" ); document.write( "Let X represent the difference between the number of heads and the number of tails
\n" ); document.write( "when a coin is tossed 41 times. Then P(X=11)=
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\n" ); document.write( "\n" ); document.write( "It is very nice,  slightly tangled probability problem.\r
\n" ); document.write( "\n" ); document.write( "I solved it  (a  TWIN  version)  once at this forum;  see my lesson\r
\n" ); document.write( "\n" ); document.write( "    - Challenging problems on Binomial distribution probability \r
\n" ); document.write( "\n" ); document.write( "(Problem 1)  in this site.  So,  it is the second time I meet this problem at the forum . . . \r
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document.write( "Let H be the number of heads and T be the number of tails.\r\n" );
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document.write( "Then we have these two equations\r\n" );
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document.write( "    H + T = 41\r\n" );
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document.write( "    H - T = 11\r\n" );
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document.write( "We solve this system elementary, using elimination method, and we get H = \"%2841%2B11%29%2F2\" = 26;  T = 15.\r\n" );
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document.write( "Now the problem is: find the probability to get 26 heads tossing a coin 41 times.\r\n" );
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document.write( "The answer is  P = \"C%5B41%5D%5E26%2A0.5%5E25%2A0.5%5E15\" = \"63432274896%2A0.5%5E41\" = 0.028845659 = 0.02885 (rounded).  \r\n" );
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