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Composite Sum Satisfaction (Posted on 2014-11-11) Difficulty: 3 of 5
Determine the largest even positive integer that cannot be written as the sum of two odd composite positive integers.

No Solution Yet Submitted by K Sengupta    
Rating: 5.0000 (1 votes)

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Solution solution | Comment 2 of 4 |

38 is the answer

For an even integer over  38:

If it's 0 mod 3, then it equals 3*3+ an odd multiple of 3;

If it's 1 mod 3, then it equals 5*5 + an odd multiple of 3;

If it's  2 mod f 3, then it's 35 plus an odd multiple of 3.

In all those cases  there exist two composite addends.

Therefore the largest possible one is 38.


In each of the above couples at least one number is a prime.

  Posted by Ady TZIDON on 2014-11-11 10:50:36
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