Question

What is the arithmetic mean of first ten natural numbers?

• A. $5.5$
• B. $6$
• C. $7.5$
• D. $10$

Answer 1

The correct option is A $5.5$

First natural no. are $1,2,3,......10$

$A.M=\frac{1+2+.....+10}{10}=\frac{\left(\frac{10\times 11}{2}\right)}{10}$ $=5.5$

[$\because$ sum of first 'n' natural no. is $\frac{n(n+1)}{2}$ ]