## PreparationThe different known domino games are played according to the following system:
| | Double-6 | | Double-9 | | Double-12 | | Double-15 | | Double-18 | | Double-21 |
Number of dominoes in the game | | 28 | | 55 | | 91 | | 136 | | 190 | | 253 |
Divisor | | 3 | | 5 | | 7 | | 9 | | 11 | | 13 | Dominoes per player with 3 Players | | 7 | | 13 | | 22 | | 34 | | 47 | | 63 |
4 Players | | 5 | | 11 | | 18 | | 27 | | 38 | | 50 |
5 Players | | 4 | | 9 | | 15 | | 22 | | 31 | | 42 |
6 Players | | 4 | | 7 | | 13 | | 19 | | 27 | | 36 |
7 Players | | 3 | | 6 | | 11 | | 17 | | 23 | | 31 |
8 Players | | 3 | | 6 | | 10 | | 15 | | 21 | | 28 |
9 Players | | 2 | | 5 | | 9 | | 13 | | 19 | | 25 |
The players sort their dominoes by differences, in order to be able to react quickly in any game situation. When played e. g. on divisor 7, the differences 1 and 8, 2 and 9, 3 and 10, 4 and 11, 5 and 12 are similarly usable, what means if it is possible to score with a domino of difference 3, it will also work with one of difference 10. That is no magic but due to the simple fact that __10__ can be split into the __needed difference (3)__ and the __divisor played (7).__ While sorting the difference of the played divisor forms the highest row; differences greater than the divisor will be reduced by the latter and belong to the group of the remaining figure. Example: the divisor is 7, the domino shows difference 9, so 9-7=2, the domino belongs to the group of differences 2. Even showing difference zero, the doubles increase the sum of the ends by the number of one of their ends because they have to be put across. So a double-four increases the sum by four. That’s why they are sorted together with the respective differences. And: doubles never decrease the sum. Continuing the example of divisor 7, the dominoes with difference 3 may be sorted in the same line with difference 4. If it is possible to score with the increase by 3, scoring will also be possible with decreasing by 4. The attentive players will have noticed that the amounts of +3 and -4 give again 7. The __Daniela Ratzek system__ of sorting the dominoes, optimizes the overview of any game situation: the dominoes with difference 3 in a line, with the smaller number to the left, and behind them the dominoes with difference 4, with the greater number to the left. |