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Railways RRB (Assistant Loco Pilot & Technician) Solved Paper-2 (2014)

  • question_answer
    If the mean of five observations x, \[x+2,\text{ }x+4,\text{ }x+6,\text{ }x+8\]is 11, then the mean of first three observations is

    A)  9                    

    B)  11       

    C)  13                              

    D)  None of these

    Correct Answer: A

    Solution :

    Here sum of 5 observations \[=x+(x+2)+(x+4)+(x+6)+(x+8)=5x+20\]\[\therefore \] Mean of total observations \[=\frac{5x+20}{5}=11\] \[\Rightarrow \]            \[5x+20=55\] \[\therefore \]    \[x=7\] \[\therefore \]  Mean of first three observations             \[=\frac{7+9+11}{3}=\frac{27}{3}=9\]


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