2. Sample Papers
  3. JEE Main & Advanced

JEE Main & Advanced Sample Paper JEE Main Sample Paper-14

  • question_answer
    If the mean and standard deviation of 20 observations \[{{X}_{1}},\,{{X}_{2}},\,{{X}_{3}},...,{{X}_{20}}\] are 50 and 10 respectively, then \[\sum\limits_{i=1}^{20}{X_{i}^{2}}\] is equal to

    A)  2600                                     

    B)  52000           

    C)  2510                                     

    D)  None of these

    Correct Answer: B

    Solution :

     \[SD\,=\sqrt{\frac{\sum{X_{i}^{2}}}{n}-{{(\overline{X})}^{2}}}\]f \[\therefore \]  \[10\,=\sqrt{\frac{\sum{X_{i}^{2}}}{20}-{{(50)}^{2}}}\] \[\Rightarrow \]               \[100=\,\frac{\sum{x_{i}^{2}}}{20}-2500\] \[\Rightarrow \]               \[\sum{x_{i}^{2}}=52000\]


You need to login to perform this action.
You will be redirected in 3 sec spinner