JEE Main & Advanced Mathematics Statistics Question Bank Mean

  • question_answer
    If the mean of the set of numbers \[{{x}_{1}},\,{{x}_{2}},\,{{x}_{3}},\,.....,\,{{x}_{n}}\] is \[\bar{x}\], then the mean of the numbers \[{{x}_{i}}+2i\], \[1\le i\le n\] is [Pb. CET 1988]

    A)                 \[\bar{x}+2n\]      

    B)             \[\bar{x}+n+1\] 

    C)                 \[\bar{x}+2\]        

    D)                 \[\bar{x}+n\]

    Correct Answer: B

    Solution :

               We know that \[\bar{x}=\frac{\sum\limits_{i=1}^{n}{{{x}_{i}}}}{n}\] i.e., \[\sum\limits_{i=1}^{n}{{{x}_{i}}}=n\bar{x}\]       \ \[\frac{\sum\limits_{i=1}^{n}{({{x}_{i}}+2i)}}{n}=\frac{\sum\limits_{i=1}^{n}{{{x}_{i}}}+2\sum\limits_{i=1}^{n}{i}}{n}=\frac{n\bar{x}+2(1+2+...n)}{n}=\frac{n\bar{x}+2\frac{n(n+1)}{2}}{n}=\bar{x}+(n+1)\]                             \[=\frac{n\bar{x}+2\frac{n(n+1)}{2}}{n}=\bar{x}+n+1\].


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