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
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a
81
b
122
c
144
d
None of these
answer is C.
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Detailed Solution
Given, σ =9Let a student obtains x marks out of 75. Then, his marks out of100 are 4x3 .Each observation multiple by 43Now, SD,σ=43×9=12Hence, variance is σ2=144