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Find the greatest prime divisor of the value of the arithmetic series
1 + 2 + 3 + \dots + 135 + 136 + 137 + 138 + 139 + 140.

 Dec 16, 2024
 #2
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So for this problem, let's use the arithmetic series formula.

 

We find the sum is \(\frac{(140+1)(70)}{2}\), which is \(141*35.\) Now that we have a factorization, we can easily find the greatest prime divisor.

 

The prime factorization is \(3*5*7*47\), so the greatest prime divisor is 47.

 

Thanks! :)

 Dec 17, 2024
edited by NotThatSmart  Dec 17, 2024

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