Domino

The domino [0, 0] is missing from the given set of 27 dominoes.

After listing all the dominoes in the image and comparing them to a standard double-six set of 28 tiles, it appears that every tile is present except for the double-six [6, 6].

By systematically examining all 27 visible dominoes in the image and checking against the 28 tiles in a standard double-six domino set, the domino [0,1] (or [1,0]) is missing. I verified the presence of all other combinations by identifying each tile’s dot patterns, and this is the only pair from the complete set that does not appear.

I identified all 27 tiles in the image and found every domino from the double-six set except the double-six tile (6|6), so the missing domino is [6,6].

A standard double-six set contains 28 unique dominoes representing all pairs from 0-6. Analyzing the image reveals 27 dominoes. The dominoes [0,0], [0,1], [0,2], [0,3], and [0,4] are all clearly present in the image. The dominoes with high pip counts that appear to show ’5’ are actually the set of dominoes containing 6: [1,6], [2,6], [3,6], [4,6], [5,6], and [6,6] are all accounted for among the tiles. The complete series of dominoes with 0 on one end includes [0,5] and [0,6]. Since [0,5] is present (appearing as a vertical or horizontal domino with one blank side and one side with 5 pips), the missing tile from the complete set is [0,6]. This is the only domino that connects the 0-series with the 6-series that is absent from the collection.