Question

Find the sum:
$3+11+19+.....+803$

Answer 1

$3+11+19+...+803$

This is in the form Arithmetic Progression.

So We Can Use the Equation in A.P to find Sum .

Here, $a=3$ , and we need to find $n=$?

So, to find $n$ , we will use the formula ...

Here, $d$ is common Difference , where $d=11-3=19-11=8$

So by using above formula ,

$803=3+(n-1)8$

$800=(n-1)8$

$n-1=800/8$

$n=101$

So, now sum is

$S=101\ast 403$

$S=40,703$

Therefore , $3+11+19+...+803=40,703$