document.write( "Question 1011646:
\n" ); document.write( "a)An integer is choosen at random from the first 200 positive integer. what is the probabililty that the integer chosen is divisible by 6 or by 8??\r
\n" ); document.write( "\n" ); document.write( "b)Three horses A,B,C are in a race; A is twice likely to win as B and B is twice as likely to win as C,what is probability that A or B wins??
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\n" ); document.write( "Question:
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\n" ); document.write( "a)An integer is choosen at random from the first 200 positive integer. what is the probabililty that the integer chosen is divisible by 6 or by 8??\r
\n" ); document.write( "\n" ); document.write( "b)Three horses A,B,C are in a race; A is twice likely to win as B and B is twice as likely to win as C,what is probability that A or B wins??
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\n" ); document.write( "Solutions:
\n" ); document.write( "note: floor(x)=[x]=largest integer that does not exceed x.
\n" ); document.write( "a)
\n" ); document.write( "between 1 and 200,
\n" ); document.write( "floor(200/6)=33 are divisible by 6
\n" ); document.write( "floor(200/8)=25 are divisible by 8
\n" ); document.write( "floor(200/24)=8 are divisible by 24 (LCM of 6 and 8)
\n" ); document.write( "So by the inclusion/exclusion principle, (33+25-8)=50 are divisible by 6 or 8.
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\n" ); document.write( "b)
\n" ); document.write( "P(A)=2P(B)
\n" ); document.write( "P(B)=2P(C)
\n" ); document.write( "=>
\n" ); document.write( "P(A)=4P(C)
\n" ); document.write( "or
\n" ); document.write( "P(A)+P(B)+P(C)=(4+2+1)P(C)=7P(C)=1
\n" ); document.write( "P(C)=1/7
\n" ); document.write( "Therefore probability that A or B wins = 1-1/7=6/7\r
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