Imagine you have a pair of cubes. You have six sides on both cube. What are the combinations that are possible? That's right, 1-6 x six. Cube number 1 can be set with the ONE pointed up and the second cube can have 1 2 3 4 5 or 6 up. Then Cube 1 can have the TWO pointing up and the second cube has six possible positions.
There are in fact 36 PERMUTATIONS (every possible arrangement, even the arrangements that appear similar). For example, 1,2 and 2,1 are the same COMBINATION, but there are two different PERMUTATIONS using these two numbers.
Here is a definition of the difference between PERMUTATIONS and COMBINATIONS
there is an important difference between permutations and combinations. In this case, for permutations the order of events is important: order 1 is different from order 2. For combinations, however, it does not matter which picture was hung first. In this example there are two permutations (A, B ≠ B, A), but only one combination (A, B = B, A).
P = the position is important (A first or B first)
1 is first or 2 is first
C = CHOICE
Learn more about dominoes by reading Mario's book