JEE Main & Advanced JEE Main Online Paper (Held On 15 April 2018) Slot-I

  • question_answer The mean of a set of 30 observations is 75. If each other observation is multiplied by a non-zero number \[\lambda \] and then each of them is decreased by 25, their mean remains the same. The \[\lambda \] is equal to                                            [JEE Online 15-04-2018]

    A) \[\frac{10}{3}\]                                  

    B) \[\frac{4}{3}\]

    C) \[\frac{1}{2}\]                        

    D) \[\frac{2}{3}\]

    Correct Answer: B

    Solution :

    Since mean is a linear operation, after taking product with the same number and subtracting the same number, the mean becomes\[75\lambda -25\]. We thus have by the condition given in the problem\[75\lambda -25=75\Rightarrow \lambda =\frac{4}{3}\].

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