The idea behind this puzzle came from Lech Pijanowski (via Martin Gardner – I don’t read Polish fluently). A standard domino set contains 28 rectangular tiles which display all the possible pairs of digits for 0 through 6. These tiles are laid out to make up a rectangle. The goal is to figure out an arrangement where all 28 tiles appear, with none duplicated or left out.
Given this patternless grid of numbers, how do you attack it? A good start is to list all the domino pairs (6-6, 6-5, 6-4, …, 1-1, 1-0, 0-0). Then search the grid for pairs that can be at only one spot. For instance, if there is only one place where two 4’s are adjacent to each other, then they must go together to make the domino 4-4. Mark all such unique pairs. Then check if there are any domino placements necessary to prevent holes in the final layout. When one of these happens, that combination cannot appear elsewhere in the grid or a tile would be duplicated. So anywhere else those two numbers are adjacent, a line can be drawn between them since they can’t appear on the same domino again.
Whenever you have a configuration like 25 with no other place in the grid where 52 and 5 appear together, then the 2 must go with one of the 5’s. So you can close off the 2 from the other tiles around it, as in 25. Another case where lines 5 may be entered in the grid is with an arrangement like 363 where 3 and 6 do not appear together elsewhere. The 6 must then be paired with one of the 3’s, so it can be marked off from the other dominoes around it, as in 363.
Keep track throughout the process of which tiles have been used. When all else fails, stoop to trial and error. (Piece of cheap advice: Start in a corner if you’ve sunk to the t.&e. stage.)
Grid A is a simple one just to whet your appetite. If you find it pleasurable, try B. It takes longer. Note that some grids may have more than one possible solution. The solver is only expected to find any one of the possible layouts. Both grids must be solved to count as a finished solution.
Send the completed puzzle (or reasonable facsimile) by February 9 to Puzzling, D Magazine, 1925 San Jacinto, Dallas, Texas 75201. At that time, a drawing will take place to determine the winners. First winner will receive a $25 cash prize. Runner-up will receive a free one-year subscription to D. Winners and completed puzzle will appear in the March issue.
Solution to last month’s puzzle
Why the TV industry serves such dead-tired visual hors d’oeuvres has finally achieved scientific precision. No need to try to immerse ya’ when Smith’s fourth law of inertia states, “A body at rest tends to watch television.”
Winner: Runner-Up
Susan Moss Mrs. Richard Bland
Dallas Richardson
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