Question

the mean of the first five natural numbers is

Answer 1

Mean= Sum of no/total nos
=> 1+2+3+4+5/5
15/5
= 3

Answer 2

Natural numbers are {1, 2, 3, 4, .......................... }

(1) First Method
write down the first five natural numbers : 1, 2, 3, 4, 5
add these up, SUM = 1 + 2 + 3 + 4 + 5 = 15
So MEAN = (SUM) / (total no.s) = 15 / 5 = 3

(2) Second method
First method will not work when the question talks about large number of numbers, say "The mean of first 100 natural numbers", so here is a great way to solve this...

you know the formula for sum of N natural number
$SUM =\frac{N(N+1)}{2}\\ \\\frac{SUM}{N} =\frac{(N + 1)}{2} \\ \\ MEAN = \frac{(N+1)}{2}$

Here N = 5, so MEAN = (5 + 1) / 2 = 6 / 2 = 3.

Answer
3