Question

Find the sum of the first 50 even natural numbers.

Answer 1

$S=2+4+6+8+...$ up to $50$ terms

$a=2,d=4-2=2$ and $n=50$

$\therefore S_n=\frac{n}{2}[2a+(n-1)d]$

$=\frac{50}{2}[2\times 2+(50-1)\times 2]$

$=50[2+49]$

$=50\times 51=2550$

$\therefore$ Sum of $50$ even natural numbers$=2550$