12th Class Mathematics Sample Paper Mathematics Olympiad - Sample Paper-3

  • question_answer
    In tossing 10 coins the probability of getting exactly 5 heads is

    A) \[\frac{193}{256}\]                   

    B) \[\frac{9}{128}\]

    C) \[\frac{1}{2}\]                          

    D) \[\frac{63}{256}\]  

    Correct Answer: D

    Solution :

    [d] Probability for a head \[=\frac{1}{2}i.e,\text{ }p=\frac{1}{2}\] \[\therefore q=\frac{1}{2}\] The probability that out of 10 coins, r coins show head \[{{=}^{10}}{{C}_{r}}{{\left( \frac{1}{2} \right)}^{r}}{{\left( \frac{1}{2} \right)}^{10-r}}\] \[\therefore \]Required probability \[{{=}^{10}}{{C}_{5}}{{\left( \frac{1}{2} \right)}^{5}}{{\left( \frac{1}{2} \right)}^{5}}\] \[=\frac{10\times 9\times 8\times 7\times 6}{1\times 2\times 3\times 4\times 5}.{{\left( \frac{1}{2} \right)}^{10}}=\frac{63}{{{2}^{8}}}=\frac{63}{256}\]


You need to login to perform this action.
You will be redirected in 3 sec spinner