Feeling Edgy?

For any connected graph in the plane,

V - E + F = 2 ,

where V is the number of vertices, E is the number of edges, and F is the number of regions.

For each connected graph, count the vertices, edges, and faces by clicking on them with the mouse. Your count is updated at the left of the workspace. Don't forget to count the outside region.

Click Next Problem to try a new graph.

To create your own connected graph, select the Create mode. You can be free with your creation, but you will have to do the counting yourself.