Question

1+2+3+4+...........................=

Answer 1

1 + 2 + 3 + 4 = 10.

∴ The answer is 10.

Answer 2

Let n be the last term
then
a =1
d= 1
Sum of n term = n/2 [2a + (n -1 ) d ]
n/2[ 2+( n-1 )1]
n/2 (2+1n-1)
n/2(1 + n).