## Chapter 9, Lesson 3

David and Ruth have learned that:

A network is a figure consisting of points (vertices) connected by lines (straight or curved, called arcs).

You can travel a network when it is possible to draw the figure without retracing any line or taking your pencil off the paper.

An even vertex has an even number of arcs meeting at the vertex.

An odd vertex has an odd number of arcs meeting at the vertex.

Today, David and Ruth learned that:

It is possible to travel a network only if there are either no odd vertices or there are exactly two odd vertices.

**Tell whether each figure can be traveled. Justify your answer. If the figure can be traveled, identify a path.**