Question

The arithmetic mean of first n natural number [RPET 1986]
A) \frac{n-1}{2} B) \frac{n+1}{2} C) \frac{n}{2} D) n

Answer 1

Hi ,

1 , 2 , 3 , .... , n are first n natural numbers.


sum of first n natural numbers = n( n + 1 )/2--( 1 )

Arithmetic mean = ( 1 ) / n

= [ n ( n + 1 ) /2 ] / n

= [ n ( n + 1 ) ]/ 2n

= ( n + 1 )/2

Therefore ,

Option ( B ) is correct

I hope this helps you.

: )