Students construct a closed curve by completing the V part of the
figure. Then, by deleting two of the points on the left side, two
more solutions may be obtained. (Deleting points on the right side
gives solutions that are reflections of the two shown here.)
are the solutions with the line segments inside the rectangle:
There is only 1 solution to the 9-dot problem.
Here are the remaining solutions to the 12-dot problem. There are 19
different solutions in all.