# Changes

## User talk:Oscarlevin

, 07:38, 12 October 2010
no edit summary
Pretty much all solutions will require multiple lines, so this is a real problem. I assume a "solution" means an answer with working, whereas an "answer" is just the answer by itself.
Below is my solution to the "7_orbs" [[7 orbs]] puzzle, which I tried to contribute:
<smallpre>:Let A = set of orbs for which there are 3 or more others the same colour.:Let B = set of orbs for which there are 1 or 2 others the same colour.:Let X = set of orbs for which there are no others the same colour.
:Goal is to prove that some orb is in A.
:Possible combinations::(using the shorthand that A denotes an orb that's in A, etc)
:A A A A A A A:A A A A A A X:A A A A A B B:A A A A A X X:A A A A B B B:A A A A B B X:A A A A X X X
:Label the orbs 1, 2, 3, 4, 5, 6, 7 and test 1&2, 3&4, 5&6.
:Comparing the results of testing those three pairs with the possible combinations, you can easily show that:
:If two tested pairs glow the same colour, all members of those pairs are in A:If only one of the three tested pairs glows, members of that pair are in A:If two tested pairs glow different colours and the other doesn't glow, orb 7 is in A:If no tested pairs glow, orb 7 is in A.
:In all cases, three tests suffice to prove that some orb is in A.
:The only other thing required is to prove that two tests are not necessarily sufficient, which is trivial.</smallpre>
Is that the sort of thing you're looking for? [[User:Zerrakhi|Zerrakhi]] 12:16, 11 October 2010 (EDT)
::: This should be fixed now. Just testing a few things out. [[User:Test1|Test1]] 22:03, 11 October 2010 (EDT)

== More questions ==

I'm wondering why only a few puzzles are in the [[:Category:Needs_solution | needs solution]] category, and likewise for other similar categories. What's special about ''those'' puzzles in particular?

Because the [[7 orbs]] puzzle is listed first on the front page, I assumed it was representative, and that all puzzles would have a hint, answer and solution in the same format. Now that I've seen that's not the case, I'm less sure about how I can contribute further. (Except by asking pointed questions, of course.) [[User:Zerrakhi|Zerrakhi]] 09:38, 12 October 2010 (EDT)
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