抄録
The purpose of this study is to present an expected value of the minimum length of the network connectivity among cities. We study two patterns. One is the minimum spanning tree on the n-points scattered on a rectangle. The expected value of the length is between 0.578√<n> and 0.707√<n>. The measured value is about 0.68√<n> by using computer. Another topic is the hierarchical tree on the n-points scattered on the p-areas divided rectangle. When the relation is p^3=(n/2)^2, the length of the hierarchical tree can be minimized.
