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Back to the Wall (Posted on 2010-04-28) Difficulty: 3 of 5


No! Not a firing squad nor the need for a continuous line to cross all line segments just once!

To each vertex labeled A to L apply a different value from 1 to 12. Let V, W, X, Y and Z be the sums of their respective surrounding vertices.

Provide at least one example where V=W=X=Y=Z, or offer a reason why this, like the continuous line, is impossible.

  Submitted by brianjn    
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Solution: (Hide)
Firstly, in offering this as a problem I set out to test if my proposal could be substantiated since the classic continuous line was an impossibility. As such I required just one solution to prove possibility.

Secondly, please take the following comments in context with the comments in the forum.

The early discussion [first 5 comments] has been made on a misinterpretation of intent. The original proposal was clearly about rectangles and not polygons ('pentagons' in this case).

There is a dirth of solutions with "1" in position "A" with each 'brick' having a total of 25, 27, 28 or 29. I ran my computer overnight but it went into "Hibernation" soon after I left it! (My QuickBASIC and his, as I understand are of different versions and mine running on a slower CPU.)

Charlie has done a revamp across 4 pages in line with my intention. I cannot doubt his claim that 23 and 24 are also sums for the rectangles as they provide a balance around 26 which he claims does not exist and I didn't find in my meagre searches.

 1  3  5  4  12  11  2  8  10  7  6  9     27 
 1  3  5  4  12  11  6  8  10  7  2  9     27 
 1  3  8  4  12  11  2  5  10  7  6  9     27 
 1  3  8  4  12  11  6  5  10  7  2  9     27 
 1  4  2  5  10  12  3  9  11  8  6  7     27 
 1  4  2  5  10  12  6  9  11  8  3  7     27 
 1  4  2  6  12  10  3  11  8  5  7  9     27 
 1  4  2  6  12  10  7  11  8  5  3  9     27 
 1  4  2  7  11  12  6  10  9  3  8  5     28 
 1  4  2  7  11  12  8  10  9  3  6  5     28 
 1  4  2  8  12  10  5  11  6  3  7  9     27 
 1  4  2  8  12  10  7  11  6  3  5  9     27 
 1  4  2  10  8  12  3  7  6  9  5  11     25 
 1  4  2  10  8  12  5  7  6  9  3  11     25 
 1  4  3  7  12  11  5  10  8  2  9  6     28 
 1  4  3  7  12  11  9  10  8  2  5  6     28 
 1  4  3  9  8  12  2  6  7  10  5  11     25 
 1  4  3  9  8  12  5  6  7  10  2  11     25 
 1  4  3  10  9  11  2  7  5  8  6  12     25 
 1  4  3  10  9  11  6  7  5  8  2  12     25 
 1  4  3  11  10  12  6  8  5  2  9  7     27 
 1  4  3  11  10  12  9  8  5  2  6  7     27 
 1  4  6  3  12  10  2  7  11  8  5  9     27 
 1  4  6  3  12  10  5  7  11  8  2  9     27 
 1  4  6  9  8  12  2  3  7  10  5  11     25 
 1  4  6  9  8  12  5  3  7  10  2  11     25 
 1  4  7  3  12  10  2  6  11  8  5  9     27 
 1  4  7  3  12  10  5  6  11  8  2  9     27 
 1  4  7  10  8  12  3  2  6  9  5  11     25 
 1  4  7  10  8  12  5  2  6  9  3  11     25 
 1  4  7  10  9  11  2  3  5  8  6  12     25 
 1  4  7  10  9  11  6  3  5  8  2  12     25 
 1  4  8  11  10  12  6  3  5  2  9  7     27 
 1  4  8  11  10  12  9  3  5  2  6  7     27 
 1  4  9  5  10  12  3  2  11  8  6  7     27 
 1  4  9  5  10  12  6  2  11  8  3  7     27 
 1  4  10  7  11  12  6  2  9  3  8  5     28 
 1  4  10  7  11  12  8  2  9  3  6  5     28 
 1  4  10  7  12  11  5  3  8  2  9  6     28 
 1  4  10  7  12  11  9  3  8  2  5  6     28 
 1  4  11  6  12  10  3  2  8  5  7  9     27 
 1  4  11  6  12  10  7  2  8  5  3  9     27 
 1  4  11  8  12  10  5  2  6  3  7  9     27 
 1  4  11  8  12  10  7  2  6  3  5  9     27 
 1  5  2  9  7  12  3  6  8  11  4  10     25 
 1  5  2  9  7  12  4  6  8  11  3  10     25 
 1  5  2  10  9  12  3  8  7  4  11  6     27 
 1  5  2  10  9  12  11  8  7  4  3  6     27 
 1  5  2  11  9  10  3  8  4  7  6  12     25 
 1  5  2  11  9  10  6  8  4  7  3  12     25 
 1  5  3  4  10  11  2  8  12  9  6  7     27 
 1  5  3  4  10  11  6  8  12  9  2  7     27 
 1  5  4  7  9  10  2  6  8  11  3  12     25 
 1  5  4  7  9  10  3  6  8  11  2  12     25 
 1  5  4  7  12  10  3  9  8  2  11  6     28 
 1  5  4  7  12  10  11  9  8  2  3  6     28 
 1  5  6  7  9  10  2  4  8  11  3  12     25 
 1  5  6  7  9  10  3  4  8  11  2  12     25 
 1  5  6  9  7  12  3  2  8  11  4  10     25 
 1  5  6  9  7  12  4  2  8  11  3  10     25 
 1  5  8  4  10  11  2  3  12  9  6  7     27 
 1  5  8  4  10  11  6  3  12  9  2  7     27 
 1  5  8  10  9  12  3  2  7  4  11  6     27 
 1  5  8  10  9  12  11  2  7  4  3  6     27 
 1  5  8  11  9  10  3  2  4  7  6  12     25 
 1  5  8  11  9  10  6  2  4  7  3  12     25 
 1  5  9  7  12  10  3  4  8  2  11  6     28 
 1  5  9  7  12  10  11  4  8  2  3  6     28 
 1  6  2  4  12  8  3  11  10  7  5  9     27 
 1  6  2  4  12  8  5  11  10  7  3  9     27 
 1  6  2  7  9  12  4  8  11  5  10  3     28 
 1  6  2  7  9  12  10  8  11  5  4  3     28 
 1  6  3  8  7  11  2  5  9  12  4  10     25 
 1  6  3  8  7  11  4  5  9  12  2  10     25 
 1  6  4  5  12  10  7  9  11  2  8  3     29 
 1  6  4  5  12  10  8  9  11  2  7  3     29 
 1  6  4  7  8  10  2  5  9  12  3  11     25 
 1  6  4  7  8  10  3  5  9  12  2  11     25 
 1  6  4  7  11  10  2  8  9  3  12  5     28 
 1  6  4  7  11  10  12  8  9  3  2  5     28 
 1  6  5  7  8  10  2  4  9  12  3  11     25 
 1  6  5  7  8  10  3  4  9  12  2  11     25 
 1  6  5  8  7  11  2  3  9  12  4  10     25 
 1  6  5  8  7  11  4  3  9  12  2  10     25 
 1  6  8  7  9  12  4  2  11  5  10  3     28 
 1  6  8  7  9  12  10  2  11  5  4  3     28 
 1  6  8  7  11  10  2  4  9  3  12  5     28 
 1  6  8  7  11  10  12  4  9  3  2  5     28 
 1  6  9  5  12  10  7  4  11  2  8  3     29 
 1  6  9  5  12  10  8  4  11  2  7  3     29 
 1  6  11  4  12  8  3  2  10  7  5  9     27 
 1  6  11  4  12  8  5  2  10  7  3  9     27 
 1  7  2  4  11  9  3  10  12  6  8  5     28 
 1  7  2  4  11  9  8  10  12  6  3  5     28 
 1  7  2  5  12  8  3  11  10  4  9  6     28 
 1  7  2  5  12  8  9  11  10  4  3  6     28 
 1  7  3  4  12  8  2  10  11  5  9  6     28 
 1  7  3  4  12  8  9  10  11  5  2  6     28 
 1  7  3  9  8  12  5  6  10  4  11  2     28 
 1  7  3  9  8  12  11  6  10  4  5  2     28 
 1  7  4  5  11  10  6  8  12  3  9  2     29 
 1  7  4  5  11  10  9  8  12  3  6  2     29 
 1  7  4  10  8  12  6  5  9  3  11  2     28 
 1  7  4  10  8  12  11  5  9  3  6  2     28 
 1  7  4  10  9  11  5  6  8  2  12  3     28 
 1  7  4  10  9  11  12  6  8  2  5  3     28 
 1  7  5  10  8  12  6  4  9  3  11  2     28 
 1  7  5  10  8  12  11  4  9  3  6  2     28 
 1  7  6  9  8  12  5  3  10  4  11  2     28 
 1  7  6  9  8  12  11  3  10  4  5  2     28 
 1  7  6  10  9  11  5  4  8  2  12  3     28 
 1  7  6  10  9  11  12  4  8  2  5  3     28 
 1  7  8  5  11  10  6  4  12  3  9  2     29 
 1  7  8  5  11  10  9  4  12  3  6  2     29 
 1  7  10  4  11  9  3  2  12  6  8  5     28 
 1  7  10  4  11  9  8  2  12  6  3  5     28 
 1  7  10  4  12  8  2  3  11  5  9  6     28 
 1  7  10  4  12  8  9  3  11  5  2  6     28 
 1  7  11  5  12  8  3  2  10  4  9  6     28 
 1  7  11  5  12  8  9  2  10  4  3  6     28 
 1  8  2  4  12  6  3  11  10  7  5  9     27 
 1  8  2  4  12  6  5  11  10  7  3  9     27 
 1  8  2  5  12  7  3  11  10  4  9  6     28 
 1  8  2  5  12  7  9  11  10  4  3  6     28 
 1  8  3  4  12  7  2  10  11  5  9  6     28 
 1  8  3  4  12  7  9  10  11  5  2  6     28 
 1  8  3  10  7  11  2  5  9  6  12  4     27 
 1  8  3  10  7  11  12  5  9  6  2  4     27 
 1  8  4  7  9  10  2  6  11  5  12  3     28 
 1  8  4  7  9  10  12  6  11  5  2  3     28 
 1  8  5  10  7  11  2  3  9  6  12  4     27 
 1  8  5  10  7  11  12  3  9  6  2  4     27 
 1  8  6  7  9  10  2  4  11  5  12  3     28 
 1  8  6  7  9  10  12  4  11  5  2  3     28 
 1  8  10  4  12  7  2  3  11  5  9  6     28 
 1  8  10  4  12  7  9  3  11  5  2  6     28 
 1  8  11  4  12  6  3  2  10  7  5  9     27 
 1  8  11  4  12  6  5  2  10  7  3  9     27 
 1  8  11  5  12  7  3  2  10  4  9  6     28 
 1  8  11  5  12  7  9  2  10  4  3  6     28 
 1  9  2  4  11  7  3  10  12  6  8  5     28 
 1  9  2  4  11  7  8  10  12  6  3  5     28 
 1  9  2  11  7  10  3  6  8  5  12  4     27 
 1  9  2  11  7  10  12  6  8  5  3  4     27 
 1  9  4  7  8  10  3  5  12  6  11  2     28 
 1  9  4  7  8  10  11  5  12  6  3  2     28 
 1  9  5  7  8  10  3  4  12  6  11  2     28 
 1  9  5  7  8  10  11  4  12  6  3  2     28 
 1  9  6  11  7  10  3  2  8  5  12  4     27 
 1  9  6  11  7  10  12  2  8  5  3  4     27 
 1  9  10  4  11  7  3  2  12  6  8  5     28 
 1  9  10  4  11  7  8  2  12  6  3  5     28 
 1  10  2  6  12  4  3  11  8  5  7  9     27 
 1  10  2  6  12  4  7  11  8  5  3  9     27 
 1  10  2  8  12  4  5  11  6  3  7  9     27 
 1  10  2  8  12  4  7  11  6  3  5  9     27 
 1  10  2  11  7  9  3  6  8  5  12  4     27 
 1  10  2  11  7  9  12  6  8  5  3  4     27 
 1  10  2  11  9  5  3  8  4  7  6  12     25 
 1  10  2  11  9  5  6  8  4  7  3  12     25 
 1  10  4  5  11  7  6  8  12  3  9  2     29 
 1  10  4  5  11  7  9  8  12  3  6  2     29 
 1  10  4  5  12  6  7  9  11  2  8  3     29 
 1  10  4  5  12  6  8  9  11  2  7  3     29 
 1  10  4  7  8  6  2  5  9  12  3  11     25 
 1  10  4  7  8  6  3  5  9  12  2  11     25 
 1  10  4  7  8  9  3  5  12  6  11  2     28 
 1  10  4  7  8  9  11  5  12  6  3  2     28 
 1  10  4  7  9  5  2  6  8  11  3  12     25 
 1  10  4  7  9  5  3  6  8  11  2  12     25 
 1  10  4  7  9  8  2  6  11  5  12  3     28 
 1  10  4  7  9  8  12  6  11  5  2  3     28 
 1  10  4  7  11  6  2  8  9  3  12  5     28 
 1  10  4  7  11  6  12  8  9  3  2  5     28 
 1  10  4  7  12  5  3  9  8  2  11  6     28 
 1  10  4  7  12  5  11  9  8  2  3  6     28 
 1  10  5  7  8  6  2  4  9  12  3  11     25 
 1  10  5  7  8  6  3  4  9  12  2  11     25 
 1  10  5  7  8  9  3  4  12  6  11  2     28 
 1  10  5  7  8  9  11  4  12  6  3  2     28 
 1  10  6  3  12  4  2  7  11  8  5  9     27 
 1  10  6  3  12  4  5  7  11  8  2  9     27 
 1  10  6  7  9  5  2  4  8  11  3  12     25 
 1  10  6  7  9  5  3  4  8  11  2  12     25 
 1  10  6  7  9  8  2  4  11  5  12  3     28 
 1  10  6  7  9  8  12  4  11  5  2  3     28 
 1  10  6  11  7  9  3  2  8  5  12  4     27 
 1  10  6  11  7  9  12  2  8  5  3  4     27 
 1  10  7  3  12  4  2  6  11  8  5  9     27 
 1  10  7  3  12  4  5  6  11  8  2  9     27 
 1  10  8  5  11  7  6  4  12  3  9  2     29 
 1  10  8  5  11  7  9  4  12  3  6  2     29 
 1  10  8  7  11  6  2  4  9  3  12  5     28 
 1  10  8  7  11  6  12  4  9  3  2  5     28 
 1  10  8  11  9  5  3  2  4  7  6  12     25 
 1  10  8  11  9  5  6  2  4  7  3  12     25 
 1  10  9  5  12  6  7  4  11  2  8  3     29 
 1  10  9  5  12  6  8  4  11  2  7  3     29 
 1  10  9  7  12  5  3  4  8  2  11  6     28 
 1  10  9  7  12  5  11  4  8  2  3  6     28 
 1  10  11  6  12  4  3  2  8  5  7  9     27 
 1  10  11  6  12  4  7  2  8  5  3  9     27 
 1  10  11  8  12  4  5  2  6  3  7  9     27 
 1  10  11  8  12  4  7  2  6  3  5  9     27 
 1  11  3  4  10  5  2  8  12  9  6  7     27 
 1  11  3  4  10  5  6  8  12  9  2  7     27 
 1  11  3  7  12  4  5  10  8  2  9  6     28 
 1  11  3  7  12  4  9  10  8  2  5  6     28 
 1  11  3  8  7  6  2  5  9  12  4  10     25 
 1  11  3  8  7  6  4  5  9  12  2  10     25 
 1  11  3  10  7  8  2  5  9  6  12  4     27 
 1  11  3  10  7  8  12  5  9  6  2  4     27 
 1  11  3  10  9  4  2  7  5  8  6  12     25 
 1  11  3  10  9  4  6  7  5  8  2  12     25 
 1  11  4  10  9  7  5  6  8  2  12  3     28 
 1  11  4  10  9  7  12  6  8  2  5  3     28 
 1  11  5  4  12  3  2  8  10  7  6  9     27 
 1  11  5  4  12  3  6  8  10  7  2  9     27 
 1  11  5  8  7  6  2  3  9  12  4  10     25 
 1  11  5  8  7  6  4  3  9  12  2  10     25 
 1  11  5  10  7  8  2  3  9  6  12  4     27 
 1  11  5  10  7  8  12  3  9  6  2  4     27 
 1  11  6  10  9  7  5  4  8  2  12  3     28 
 1  11  6  10  9  7  12  4  8  2  5  3     28 
 1  11  7  10  9  4  2  3  5  8  6  12     25 
 1  11  7  10  9  4  6  3  5  8  2  12     25 
 1  11  8  4  10  5  2  3  12  9  6  7     27 
 1  11  8  4  10  5  6  3  12  9  2  7     27 
 1  11  8  4  12  3  2  5  10  7  6  9     27 
 1  11  8  4  12  3  6  5  10  7  2  9     27 
The following is my program listing, which other than values for W, Y and Z in Charlie's program, is very similar to his having been built on a model which he so often uses.
CLS
DIM used(15)
OPEN "WALL.TXT" FOR OUTPUT AS #1
FOR a = 1 TO 12
IF used(a) = 0 THEN
used(a) = 1
FOR b = 1 TO 12
IF used(b) = 0 THEN
used(b) = 1
FOR c = 1 TO 12
IF used(c) = 0 THEN
used(c) = 1
FOR d = 1 TO 12
IF used(d) = 0 THEN
used(d) = 1
FOR e = 1 TO 12
IF used(e) = 0 THEN
used(e) = 1
FOR f = 1 TO 12
IF used(f) = 0 THEN
used(f) = 1
FOR g = 1 TO 12
IF used(g) = 0 THEN
used(g) = 1
FOR h = 1 TO 12
IF used(h) = 0 THEN
used(h) = 1
FOR i = 1 TO 12
IF used(i) = 0 THEN
used(i) = 1
FOR j = 1 TO 12
IF used(j) = 0 THEN
used(j) = 1
FOR k = 1 TO 12
IF used(k) = 0 THEN
used(k) = 1
FOR l = 1 TO 12
IF used(l) = 0 THEN
used(l) = 1
v = a + b + e + f
w = b + c + f + h
x = c + d + h + i
y = e + g + j + k
z = g + i + k + l
LOCATE 1, 1: PRINT a; b; c; d; e; f; g; h; i; j; k; l, v; w; x; y; z
IF v = w AND w = x AND x = y AND y = z THEN
PRINT a; b; c; d; e; f; g; h; i; j; k; l, v
PRINT #1, a; b; c; d; e; f; g; h; i; j; k; l, v
END IF


used(l) = 0
END IF
NEXT
used(k) = 0
END IF
NEXT
used(j) = 0
END IF
NEXT
used(i) = 0
END IF
NEXT
used(h) = 0
END IF
NEXT
used(g) = 0
END IF
NEXT
used(f) = 0
END IF
NEXT
used(e) = 0
END IF
NEXT
used(d) = 0
END IF
NEXT
used(c) = 0
END IF
NEXT
used(b) = 0
END IF
NEXT
used(a) = 0
END IF
NEXT

CLOSE 1

Comments: ( You must be logged in to post comments.)
  Subject Author Date
efficiencyed bottemiller2010-05-04 11:45:15
re(2): Impossibilitybrianjn2010-05-02 04:12:54
re: ImpossibilityCharlie2010-05-01 13:26:15
Impossibilitybrianjn2010-05-01 06:19:29
four-square solutionsed bottemiller2010-04-30 20:41:02
re: If rectangle sums only of counters...Charlie2010-04-30 03:21:39
Solutionre(4): Misinterpretation -- listing continuedCharlie2010-04-30 03:17:16
Solutionre(3): Misinterpretation -- listing continuedCharlie2010-04-30 03:16:09
Solutionre(2): Misinterpretation -- listing continuedCharlie2010-04-30 03:14:39
Solutionre: MisinterpretationCharlie2010-04-30 03:13:18
Misinterpretationbrianjn2010-04-30 01:15:38
If rectangle sums only of counters...ed bottemiller2010-04-29 16:40:14
Reasons and Searchesed bottemiller2010-04-28 19:37:08
vertices, etc.ted bottemiller2010-04-28 17:55:10
re(2): computer solution -- the programCharlie2010-04-28 13:53:06
Solutionre: computer solution -- the part that got cut offCharlie2010-04-28 13:51:48
Solutioncomputer solutionCharlie2010-04-28 13:49:45
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