| If I needed to describe the distance between 
                    two cities, I could provide an answer consisting of a single 
                    number in miles, kilometers, or some other unit of linear 
                    measurement. However, if I were to describe how to travel 
                    from one city to another, I would have to provide more 
                    information than just the distance between those two cities; 
                    I would also have to provide information about the 
                    direction to travel, as well.  The kind of information that expresses a 
                    single dimension, such as linear distance, is called a 
                    scalar quantity in mathematics. Scalar numbers are the 
                    kind of numbers you've used in most all of your mathematical 
                    applications so far. The voltage produced by a battery, for 
                    example, is a scalar quantity. So is the resistance of a 
                    piece of wire (ohms), or the current through it (amps).  
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