Question

The variance of first $20$ natural numbers is

• A. 133/4
• B. 279/12
• C. 133/2
• D. 399/4

Answer 1

Answer: (A)

Variance of $n$ natural numbers
$=\frac{n^2-1}{12}=\frac{(20{)}^2-1}{12}[\because n=20]$
$=\frac{400-1}{12}=\frac{399}{12}=\frac{133}{4}$