The marks of some students were listed out of 75.The SD of marks was found to be 9. Subsequently the marks were raised to a maximum of 100 and variance of new marks was calculated. The new variance is

The marks of some students were listed out of 75.The SD of marks was found to be 9. Subsequently the marks were raised to a maximum of 100 and variance of new marks was calculated. The new variance is

  1. A

    81

  2. B

    122

  3. C

    144

  4. D

    None of these

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    Solution:

    Given, σ =9
    Let a student obtains x marks out of  75. Then, his marks out of

    100 are 4x3 .Each observation multiple by 43

    Now, SD,σ=43×9=12

    Hence, variance is σ2=144

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