The sum of first 25 odd natural numbers is

Sum of for 25 odd numbers :- 

Let S denote the sum of  first 25 odd numbers 

Here number are 1, 3, 5, 7, 9 --------- 49.

Here  first term is 1 

last term is 49

Common difference d is 2 

n = 25

i. e Sum $=\frac{n}{2}\left(a+T_{n}\right)$

$=\frac{25}{2}(1+49)$

$=\frac{25 \times 50}{2}$

$=25 \times 25$

i.e sum of first 25 odd numbers = 625.