Domino

All 28 dominoes from a double-six set are present except for the double blank (0-0). I have systematically checked every other domino and it is accounted for on...

Comparing the visible dominoes against all 28 combinations in a double-six set, every pair is represented except the 3-5 domino.

Scanning all 27 dominoes on the board, the blank-ended dominoes present are 0-0, 0-1, 0-2, 0-3, 0-4, and 0-6. Every other combination from the double-six set ap...

Counted 27 dominoes on the board. Systematically checking all 28 combinations 0-0 through 6-6, the 0-6 domino (blank paired with six) never appears in any orien...

The board contains 27 dominoes. Checking every pair systematically, the 4-6 domino never appears, so it must be the excluded one.