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  • An urn contains 5 red balls and 5 black balls. In the first draw, one ball is plcked at random and discarded without noticing its colour. The probability to get a red ball in the second draw is

An urn contains 5 red balls and 5 black balls. In the first draw, one ball is plcked at random and discarded without noticing its colour. The probability to get a red ball in the second draw is

Option: 1

\frac{1}{2}


Option: 2

\frac{4}{9}


Option: 3

\frac{5}{9}


Option: 4

\frac{6}{9}


Answers (1)

best_answer

5 Red balls and 5 Black balls.
One ball discarded in first draw


From the above tree diagram, we get the probability of favourable branches (getting Red ball in second attempt) as;
\mathrm{Req. Prob. =\left ( R\, in \, I^{st}\, and\, R\, in\, II^{nd} \right )\, or\, \left ( B\, in \, I^{st}\, and\, R\, in\, II^{nd} \right )}
\mathrm{=\left(\frac{1}{2} \times \frac{4}{9}\right)+\left(\frac{1}{2} \times \frac{5}{9}\right)}
\mathrm{ =\frac{4}{18}+\frac{5}{18}}
\mathrm{ =\frac{1}{2}}

 

Posted by

Kuldeep Maurya

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