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Home  >>  CBSE XII  >>  Math  >>  Probability
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A bag contains 5 red and 3 blue balls.The probability that exactly two of the three balls were red,the first ball being red,is

$\begin{array}{1 1}(A)\;\large\frac{1}{3}\\(B)\;\large\frac{4}{7}\\(C)\;\large\frac{15}{28}\\(D)\;\large\frac{5}{28}\end{array} $

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1 Answer

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Options:To find p(2Balls red/first ball is red)We take sample space where the first ball is Red =s(\(R\;B\;R\;,R\;R\;R\;,R\;B\;B\;,R\;R\;B)\)
\(Frome\; the\; given\; set\; there\; are\; 2\; cases\; in\; which\; there\; are\; 2\; red\; balls\;so\;p(R\;B\;R\;\cup\;R\;R\;B)\)
=\(\Large\frac{3}{7}\;\times\;\frac{4}{6}\;+\;\frac{4}{7}\;\times\;\frac{3}{6}\;=\;\frac{24}{7}\;=\;\frac{4}{7}\)
\('B'\; is\; correct\)
 
 

 

answered Feb 21, 2013 by poojasapani_1
edited Jun 4, 2013 by poojasapani_1
 

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