Question

find the sum of first 80 natural number​

Answer 1

A.P: 1,2,3,4.....80

a=1, d=1, n=80

a^n = a + (n-1)d

= 1 + (80-1)1

= 1 + 79

= 80

S^n = n/2 (a + a^n)

= 80/2 (1 + 80)

= 40(81)

= 3204

Hope it helps!!! :)

Answer 2

As we know the formula, n/2×(1+n),so according to it

=(80/2)×1+80

=40×81

=3240 answer.