This report is concerned with the observation that many teenagers and adults are unable to apply arithmetic even when they know how to perform the operations. It is speculated that this is probably due to not having been taught when to use the fundamental operations. Examples of types of "real" problems which require the various operations for their solution are presented. The applications of each operation are grouped by addition, subtraction, multiplication, and division and a model example is included with each category. The use of models for operations is considered important because they: (1) help to show when to use a given operation; (2) show important relationships between arithmetic studied and the real world; (3) can be used to develop and illustrate properties of operations; (4) can be used to check answers; (5) help to classify the applications of arithmetic; and (6) help to explain concepts in higher mathematics. (MP)