What is $18+22+26+30+...+50=$ ?

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Answer 1 · 2017-12-06T08:45:45

$S_n=306$

Assuming that $n_1=18, n_2=22, ...$

$22-18=4$
$26-22=4$

$18+(n-1)4=18+4n-4=4n+14$

$4n+14=50$

$4n=36$

$n=36/4=9$

The last term occurs at $n=9$

$S_n=1/2n(a+l)$

$n$ = number of terms
$a$ = first term
$l$ = last term

$S_n=1/2 *9(18+50)$

$=4.5(68)$

$=306$

What is 18+22+26+30+...+50=18+22+26+30+...+50=?