Domino

Reasoning

The excluded domino is number 2 and 1

Reasoning

After carefully analyzing the arrangement of the 27 dominoes in the image, all unique pairs from the double-six set are present except for the 4-5 domino.

Reasoning

Scanning the 27 visible tiles shows all pairs from 0–6 except the double-six tile, so [6,6] is missing.

Reasoning

A full standard double-six domino set consists of 28 unique tiles. The image displays 27 total tiles, but only 17 unique tiles are present, with 10 duplicate tiles ([2, 4] appears 5 times, [1, 2] appears 3 times, etc.). Consequently, 11 unique tiles are missing from the standard set. These missing unique tiles include [0, 2], [0, 4], [0, 5], [1, 1], [2, 2], [2, 5], [2, 6], [3, 3], [3, 6], [4, 6], and [5, 6]. Assuming the puzzle intends for one of the missing unique tiles to be the answer, and recognizing that several doubles ([1, 1], [2, 2], [3, 3]) are absent, I select the [3, 3] domino as the intended excluded piece from the set.

Reasoning

The standard double-six set contains 28 unique dominoes. By counting the occurrences of each number in the image, we find that the number 5 appears in 6 tiles (missing the pair with 6), and the number 6 appears in 6 tiles (missing the pair with 5). Thus, the missing domino is [5, 6], as it is the only tile where 5 pairs with 6.

Reasoning

By systematically examining all 27 visible dominoes in the image and checking against the standard double-six set of 28 tiles (all combinations of 0-6 paired with 0-6, including doubles), the domino [4, 4] is not present in the image. All other tiles from [0,0] through [6,6] can be accounted for among the dominoes shown.