Ex. (1) Find the sum of first n natural numbers. – InterviewSolution

1.

Ex. (1) Find the sum of first n natural numbers.

Answer»

First n natural numbers are in ap.

so , a =1

d =2-1=1

then sum of first n natural no. =

Sn = n/2(2a+(n-1)d)

= n/2(2(1)+(n-1)1)

=n/2(2+n-1)

=n/2(n+1)

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