Verify Whether $1 + 2 + 3 + \ldots + n = \frac { n } { 2 } ( n + 1 )$

Verify whether $1 + 2 + 3 + \ldots + n = \frac { n } { 2 } ( n + 1 )$ is true for $n = 3$ .

A) yes
B) no