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Make it equal (Posted on 2010-05-26) |
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Divide the set {1,2,3,4, ....,n} into three disjoint subsets A , B , C whose sums of elements are equal.
For what values of n it is feasible?
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Submitted by Ady TZIDON
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Rating: 3.0000 (2 votes)
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Solution:
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(Hide)
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Let us show that once a solution exist for (1,2,3,... n), creating a 3E-Partition for (1,2,3,...n+2, n+3) is trivial .
My proof:
Let the 3E-Partition for sum(n) be S1, S2, S3.
We have to add 3 additional numbers n+1 , n+2 ,n+3 i.e. to increase each subset by n+2.
We will replace number 1 (present in one of the subsets, say S2) by n+3; the number n+2 will go to another subset (e.g. S1) without replacement.
Two unassigned numbers 1 and n+1 go to the last subset
(S3 in our example).
Since existence of a solution for n=5 and 4=6 was shown de facto, the process of full induction is concluded.
Ans:5,6.8.9.11,12.....(3n-1),(3n),....
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