Students may discover "measure the area of a polygonal figure" as a measure of degree of scattering. Another students may think of "measure of the length of all segments connecting two points," and still another may do "measure the radius of the smallest circle including all points." These methods of measure have advantages and disadvantages. The teacher can help students see both the advantages and disadvantages in generalizing the proposed methods.Ways to develop are open.After students solved the problem, they can develop new problems by changing the conditions or attributions of the original problem. When we emphasize this aspect of "from problem to problem"(Takeuchi & Sawada, 1984), the problem can be said that ways to developareopen. An example below, "matchstick problem," is taken from problems used in the US-Japan comparative study on mathematical problem solving (Miwa,1992).