# Using Technology in Number Sense

Instructor: Michael Eckert

Michael has a Bachelor's in Environmental Chemistry and Integrative Science. He has extensive experience in working with college academic support services as an instructor of mathematics, physics, chemistry and biology.

We can use a scientific calculator for a variety of purposes in terms of number sense. In this lesson, we will see how the TI-84 scientific calculator can be used in straightforward financial computation problems.

## Using the Correct Mode for the TI-84

Often in problems of finance, a great number of computations of a function need to be made. In this lesson we will provide a couple of examples of how we might use a Texas Instruments TI-84 scientific calculator in a number sense. We will be using it to quickly compute values for variables for functions in two problems in finance.

Before we use our calculator, it is best that we set the MODE of our calculator accordingly (i.e. ensuring that we are in normal functioning mode as opposed to engineering or scientific mode, that we are dealing with real numbers as opposed to imaginary numbers, etc). MODE should be set as follows:

## Using The TI-84 for Quick Computation of a Function

Again, we want to illustrate how the TI-84 scientific calculator may be used to do computations of a function's variables through a couple of straight forward financial problems -specifically regarding:

1. Cost per Unit and
2. Compounding Interest

## Cost per Unit

In this example, we will be looking at an equation in the form of y = mx + b, that of a straight line, to model and predict cost per number of units of a good or service. In this case, y = the total cost of some total number of units of a good or service, x = the total number of units of that good or service and m = the cost per unit of that said good or service. For our purposes here, b is merely a constant representing no inherent value; therefore, it can equal zero and be disregarded. If we wish to model the total cost of a total number of units of a good or service produced, given that each unit produced has a cost of \$2, we can say that y = 2x, where again, y will be the total cost, x will be the number of units produced and 2 is the cost per unit. If we wished to calculate (by hand) the total cost to produce 500 units, we would merely substitute 500 for x and solve for y, where y = 2 (500) = \$1000; however, to solve for y through several values of x quickly and without error, we can implement the TI-84 calculator. Before we do anything else with our calculator, we will want to set our TBLSET starting as follows (with x-values starting at 1 and listed in increments of 1, representing our number of units):

Next, we merely need to place the equation y = 2x into the Y= as shown below:

Once we have inputted this function into the Y=, we press the TABLE to obtain our data. In other words, the TI-84 will automatically run x-values and compute corresponding y-values. We then only need to scroll down the TABLE. For instance, if we wished to know how much it would cost (cost being represented in the 2nd or Y1 column below) to produce x = 1 to 7 units (represented in the 1st or x column below), we would have:

And for x = 8-14 units, we would have:

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