When Dominic arranges his dominoes, for two to be next to each other the ends that touch must have the same number of pips on them. For example, he could place:
Suppose Dominic places his dominoes on the right into the hexagon shown below.
How many of the other five dominoes can be placed in a completed hexagon next to ?
If you liked this problem, here is an NRICH task that challenges you to use similar mathematical ideas.