Question

find the value of 1+2+3+4+5+6. Given that 1+2+3+4+...+n=n(n+1) / 2

Answer 1

n=6
6(6+1)/2=6*7/2=3*7=21

Answer 2

$\mathbf{n = number \: of \: terms}$

In Question, Number of terms Is 6




$\bold{Applying \: Given \: Formula,}$

$s_{6} = \frac{6}{2} (6 + 1) \\ \\ = > s_{6} = 3(7) \\ \\ = > s_{6} = 21$





$\mathbf{ Sum \: is \: \: 21}$