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Railways Sample Paper RRBs Assistant Loco Pilot and Technician CBT STAGE-I Sample Paper-4

  • question_answer
    If the mean of five observations x, \[x+2,\]\[x+4,\]\[x+6,\]\[x+8\] 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 \[=\frac{5x+20}{5}=11\] \[\Rightarrow \]   \[5x+20=55\Rightarrow x=7\] \[\therefore \] Mean of first three observations \[=\,\frac{7+9+11}{3}=\frac{27}{3}=9\]


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