Answer :

Hi !

An AP is formed ,

1,2,3 .....

a = 1 , d = 1 , n = 9

Sn = n/2 [ 2a + [n-1]d ]
      
       = 9/2 [ 2 + 8 ]
       = 45

Sum of the first 9 natural numbers = 45

Sum of n natural no = n (n+1)/2 = 9 x 10/2 = 45.



thank u.

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