How many pieces there in domino set?

A standard dominoes set, known as a double-six set, has the following 28 pieces:

• 0-0
• 0-1, 1-1
• 0-2, 1-2, 2-2
• 0-3, 1-3, 2-3, 3-3
• 0-4, 1-4, 2-4, 3-4, 4-4
• 0-5, 1-5, 2-5, 3-5, 4-5, 5-5
• 0-6, 1-6, 2-6, 3-6, 4-6, 5-6, 6-6

Extended sets of dominoes also exist. The most common extended set is the double-twelve set, which has 91 pieces. Other, less common extended dominoes sets are the double-nine set, which has 55 pieces, the double-fifteen set, which has 136 pieces, and the double-eighteen set, which has 190 pieces.

A double-nine set of dominoes has the same 28 pieces that are in the double-six set plus...

• 0-7, 1-7, 2-7, 3-7, 4-7, 5-7, 6-7, 7-7
• 0-8, 1-8, 2-8, 3-8, 4-8, 5-8, 6-8, 7-8, 8-8
• 0-9, 1-9, 2-9, 3-9, 4-9, 5-9, 6-9, 7-9, 8-9, 9-9

A double-twelve set of dominoes has the same 55 pieces that are in the double-nine set plus...

• 0-10, 1-10, 2-10, 3-10, 4-10, 5-10, 6-10, 7-10, 8-10, 9-10, 10-10
• 0-11, 1-11, 2-11, 3-11, 4-11, 5-11, 6-11, 7-11, 8-11, 9-11, 10-11, 11-11
• 0-12, 1-12, 2-12, 3-12, 4-12, 5-12, 6-12, 7-12, 8-12, 9-12, 10-12, 11-12, 12-12

And so on....