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# help

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For which positive integer n do we have $$1 + 2 + 3 + 4 + \ldots + n = 10 \times n ?$$

Jul 6, 2020

#1
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The sum of the first n integers is given by n*(n+1)/2

So you have   n*(n+1)/2 = 10*n

Solve for n.

Jul 6, 2020