Dominoes have a long history as playing pieces for a variety of games, and they come in sets of many sizes. The size of the domino set depends on the largest number of dots, or pips, appearing on one side of the domino. A set of dominoes will have anywhere from 28 to 190 pieces.
Most evidence points to dominoes having been created by the Chinese, some time before A.D. 1120, when the official invention is credited to a statesman who presented a set of dominoes to Emperor Hui Tsung.
European dominoes, which are the variety most commonly found today, were probably introduced around or before the early 18th century. They moved from Italy to France, Great Britain and beyond.
A set of double-six dominoes, the most common set available, contains 28 dominoes with every possible combination of halves containing from zero to six dots on each side. The pieces in a double-six set are 0-0, 0-1, 0-2, 0-3, 0-4, 0-5, 0-6, 1-1, 1-2, 1-3, 1-4, 1-5, 1-6, 2-2, 2-3, 2-4, 2-5, 2-6, 3-3, 3-4, 3-5, 3-6, 4-4, 4-5, 4-6, 5-5, 5-6, 6-6.
A faster way of figuring out how many dominoes are in a set is by using a formula. When looking at the above list of dominoes, you notice that there are seven dominoes in the first set starting with 0, six starting with 1, five starting with 2, and so on to just one domino starting with 6. The total number of dominoes in the set is then 7+6+5+4+3+2+1=28.
The formula to find the number of dominoes in a set is (n+1)(n+2)/2, when n is the biggest number of dots that appears on one side of a domino.
Dominoes also come in larger-sized sets. Double-nine dominoes are the next biggest set, and they contain 55 dominoes. There are 91 dominoes in a set of double 12s, and 136 in a set of double-15s. The largest commercially available set of dominoes is double18s, which consists of 190 dominoes.
A number of games can be played with a set of dominoes. The most common is one in which players each draw a certain number of dominoes from which to play, and lay each new domino so it touches another domino with an end of the same number. Scoring depends on the game variation, but usually the hand ends when one player has played all his pieces. Other players are penalized for the pieces they still hold.