Question

1+2+3+4+5+............+n.....find the sum of ...these numbers.......

Answer 1

1+2+3+4+5+.......+n
a=1 d=1
Sum = n/2 x (2a + (n-1)d )
sum= n/2 x (2 + (n-1)1 )
= n/2 x (n + 1)

Answer 2

.. Sum of series of natural numbers is given by
S=n(n+1) /2
Where n is the nuber upto which sum is required...
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