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How many distinct sums can be obtained by adding three different numbers from the set {3, 6, 9, ... ,27 , 30 \(, 33, 36, 39, 42\)}?

 Jan 24, 2022
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Its just the multiples of 3 from the smallest possible sum to the largest. 

 

From 3 + 6 + 9 = 18, to 36 + 39 + 42 = 117.

This is from the 6th multiple of 3, to the 39th multiple of 3.

6 - 5 = 1, 39 - 5 = 34

 

There are 34 distinct sums.

 Jan 24, 2022

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