In my last school-class I did a logic-test with 48 exercises about finding the missing dominoes. I'm sure about 47, but this one broke my head, and I don't know yet the answer:
It could be anything but let's guess:
You have a total of 15 on the inside circle and 12 on the outside circle.
So say they have to add up to the same number for some obscure reason.
Remember it could be anything - so let's take a wild pot shot at:
We have 2 dominoes that total 8 and two that total 4 and one that totals 3.
So for symmetry, lets say the missing domino has to total 3.
So it's blank on the inside circle and 3 on the outside circle.
For a total of 15 on both the inside and outside circle and two matching sums all around.