How did Phoebe group the matchsticks that she drew?
How did the others, Alice and Luke, group their matchsticks?

In the follow-up activities draw them out for yourself and notice how YOUR drawings develop. Always begin with simple cases and try to PREDICT what will happen.

Look for patterns.
How can you describe the lines? Horizontally? Vertically?
Try to understand why the patterns develop in the ways that they do.