JEE MATHEMATICS MCQ: STATISTICS

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The average marks of boys in a class is 52 and that of girls is 42. The average marks of boys and girls combined is 50. The percentage of boys in the class is

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Correct option: C

80\%

Option C (

80\%

) is correct because it is the percentage of boys calculated using the weighted average of the marks.

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If the mean of a set of observations

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\bar X,

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{x_i} + 2\;i;i = 1,\;2, \ldots ,n

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the s.d. of the new set of observations will be