Question

The sum of all natural numbers from 1 to 25

Answer 1

sum of all natural numbers is equal to n(n+1)/2
sum of first 25 natural numbers is equal to 25(25+1)/2
sum of first 25 natural numbers is equal to 25×13
sum of first 25 natural numbers is equal to 325

Answer 2

a=1
d=1
Sn= n/2(2a+(n-1)d)
=25/2(2×1+(25-1)1)
=25/2(26)
=25×13
=325
that's it.....