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B
n2+112
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C
n2−16
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D
n2−112
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Solution
The correct option is Dn2−112 First n natural number are, x=1,2,3,.............n So mean of first n natural number is ¯x=∑xin=n+12 ∴ variance, σ2=∑x2in−(¯x)2 =16n(n+1)(2n+1)n−(n+12)2=112(n+1)(n−1)=n2−112