CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2010

  • question_answer
    The arithmetic mean of 7 consecutive integers starting with a is m. Then, the arithmetic mean of 11 consecutive integers starting with \[a+2\]is

    A)  \[2a\]                                  

    B)  \[2m\]

    C)  \[a+4\]                               

    D)  \[m+4\]

    E) \[a+m+2\]

    Correct Answer: D

    Solution :

    \[\because \]\[\frac{\begin{align}   & a+(a+1)+(a+2)+(a+3)+(a+4) \\  & \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,+(a+5)+(a+6) \\ \end{align}}{7}\] \[=m\] \[\Rightarrow \]               \[\frac{7a+21}{7}=m\] \[\Rightarrow \]               \[a=\frac{7m-21}{7}\] \[\therefore \]\[(a+2)+(a+3)+(a+4)+(a+5)\]\[+(a+6)+(a+7)\] \[\begin{align}   & \underline{\begin{align}   & \,\,\,\,\,\,\,\,\,\,\,\,+(a+8)+(a+9)+(a+10)+(a+11) \\  & \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,+(a+12) \\ \end{align}} \\  & \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,11 \\ \end{align}\] \[=\frac{11a+77}{11}\] \[=\frac{11\left( \frac{7m-21}{7} \right)+77}{11}\] \[=\frac{11(m-3)+77}{11}\] \[=\frac{11m-33+77}{11}=\frac{11m+44}{11}\] \[=m+4\]


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