How do you find the sum of the series $k$ from k=1 to 20?

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Answer 1 · 2016-11-10T13:59:14

$sum_(k=1)^20 k = 210$

We need the standard formula $sum_(r=1)^n r=1/2n(n+1)$

$:. sum_(k=1)^20 k = 1/2(20)(20+1)$
$:. sum_(k=1)^20 k = 1/2(20)(21)$
$:. sum_(k=1)^20 k = 210$

How do you find the sum of the series kk from k=1 to 20?