The Minnesota School Mathematics and Science Teaching (MINNEMAST) Project is characterized by its emphasis on the coordination of mathematics and science in the elementary school curriculum. Units are planned to provide children with activities in which they learn various concepts from both subject areas. Each subject is used to support and reinforce the other where appropriate, with common techniques and concepts being sought and exploited. Content is presented in story fashion. The stories serve to introduce concepts and lead to activities. Imbedded in the pictures that accompany the stories are examples of the concepts presented. This unit is designed to provide an adequate background for the presentation of the number line in the next unit. Elementary geometric concepts are presented (or reviewed) such as point, line, etc. Intersection is treated in order to establish the concept that "the interpretation of addition as union" is predicated on the presence of disjoint sets. Worksheets and commentaries to the teacher are provided and additional activities are suggested. (JP)