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Operations Research




                    Notes              help in useful analysis. Moreover, they help in easy observation, description and prediction.
                                       However, they over rule any manipulation.

                                       There are two types of Physical Models:
                                       (i)  Iconic Models:  An image or likeness of an object or process is Icon. These models
                                            represent the system as it is by scaling it up or down. Even though  use of these
                                            models in the area of management appears to be narrow, their usefulness is seen in
                                            the field of engineering and science. For example,

                                            (a)  In the field of R&D, prototype of the product is developed and tested to know
                                                 the workability of the new product development.

                                            (b)  Photographs, portraits, drawings are the good example of iconic types. These
                                                 models help in testifying the samples thus avoiding fullscale designing and
                                                 probable loss.
                                       (ii)  Analogue Models: These models are closely associated with iconic models. However,
                                            they are not the replicas of system or process. The analogue, in constructing these
                                            models, help in analyzing the issues and forces which are in the system or process.
                                            Because, these models use ‘one set of properties’ which is ‘analogous to another set
                                            of properties.’ For example, kids, toys, rail-road models, etc.
                                   (2)  Symbolic Models:  Symbolic Models  use letters,  numbers, figures to represent decision
                                       variables of the system. There are two types of Symbolic Models—Verbal Models and
                                       Mathematical Models.

                                       (a)  Verbal Models: These models describe a situation in written or spoken language.
                                            Written sentences, books, etc., are examples of a verbal model.

                                       (b)  Mathematical Models:  Mathematical symbols are used to represent a problem or a
                                            system under these types  of models. Rules of mathematics enable the builder to
                                            make the models more abstract and precise. There are two types of Mathematical
                                            Models—Deterministic Models and Probabilistic Models.
                                            (i)  Deterministic Models: The exact statement of variables and their relationships
                                                 are made  under these  models. The  coefficients used for the mathematical
                                                 formulation are known and are constant with certainty.  So, to  say, with  a
                                                 given  set  of  data  the  answer  will  always  be  the  same.  For  instance,
                                                 determination of the break-even sales volume (BEP), the volume where the
                                                 total cost equals the total sales revenue earned pertaining to a product.
                                                 The sales revenue line is determined by using an equation.

                                                          TSR = (SV) (PU)
                                                 where,   TSR = Total Sales revenue

                                                           SV = Sales Volume
                                                           PU = Price per Unit
                                                 The total cost line is represented as:

                                                           TC = TFC + SV (VC)
                                                           TC = Total Cost
                                                         TFC = Total Fixed Cost





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