RAJASTHAN ­ PET Rajasthan PET Solved Paper-2005

  • question_answer
    Between two players a coin is tossed 4 times. The probability that both players get equal number of heads, is

    A)  \[\frac{1}{16}\]

    B)  \[\frac{5}{256}\]

    C)  \[\frac{35}{128}\]            

    D)  None of these

    Correct Answer: C

    Solution :

     Both players can get equal number of heads 0, 1, 2, 3 and 4.          \[\therefore \]\[{{P}_{1}}\] (both players get 0 head) \[=\frac{1}{16}\times \frac{1}{16}\] \[{{P}_{2}}\] (both players get 1 head) \[=\frac{4}{16}\times \frac{4}{16}\] \[{{P}_{3}}\] (both players get 2 heads) \[=\frac{6}{16}\times \frac{6}{16}\] \[{{P}_{4}}\] (both players get 3 heads) \[=\frac{4}{16}\times \frac{4}{16}\] \[{{P}_{5}}\] (both players get 4 heads) \[=\frac{1}{16}\times \frac{1}{16}\] \[\therefore \]Required probability \[P={{P}_{1}}+{{P}_{2}}+{{P}_{3}}+{{P}_{4}}+{{P}_{5}}\] \[=\frac{1}{16\times 16}+\frac{16}{16\times 16}+\frac{36}{16\times 16}\] \[+\frac{16}{16\times 16}+\frac{1}{16\times 16}\] \[=\frac{1+16+36+16+1}{16\times 16}=\frac{70}{16\times 16}=\frac{35}{128}\]


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