This is the ninth in a series of ten self-contained units designed for use by students in ninth grade general mathematics classes. This unit is divided into six sections dealing with different concepts involving positive and negative numbers. Some concepts presented include positive and negative integers, addition and subtraction, multiplication, absolute value, and rational numbers. Though the topics are standard they are dealt with in non-traditional methods emphasizing discovery learning. Many exercises, diagrams, and topics for discussion are included. (CT)