How do you find the sum of the series $i$ from i=1 to 18?

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Answer 1 · 2016-11-13T22:46:47

$sum_(i=1)^18 i = 171$

Using the standard results:
$sum_(r=1)^n r = 1/2n(n+1)$

We have;

$sum_(i=1)^18 i = 1/2(18)(18+1)$
$:. sum_(i=1)^18 i = 1/2(18)(19)$
$:. sum_(i=1)^18 i = 171$

How do you find the sum of the series ii from i=1 to 18?