Spreadsheet Math: Making a Business Plan
In this performance task, students again organize their information into rows and columns, create a graph, but also learn how to use basic formulas. The goal of this activity is to determine the total start up (or base) cost for running a business as well as the monthly costs, plus the total cost for the business after a year of operation. The underlying concept is to apply the equation y = mx + b as (total cost) = (monthly cost) • (time) + (base cost)
Through this process, students learn how to
- sum values entered in multiple cells
- reference cells in formulas
- copy & paste or drag autofill formulas
- publish and embed their work to the web
To start the activity, I like to have my students give me a list of possible businesses I could decide to start and then choose one of them. They decide which they would like to see worked out as an example. Whichever one they choose however, they are not allowed to do themselves. I then hold a class discussion of what expenses the business might encounter and then categorize them as one-time (or base) expenses and monthly expenses.
Once we reach an adequate sized list of expenses and costs, it comes time to add them all together and try to create a single function to represent the total cost, which we do by first labeling each expense
and then plugging it into the equation. (If you wanted, you could also make a comment here about composite functions, but it’s not necessary.)
At this point, we are ready to begin transferring our information into a spreadsheet to simplify and automate our calculations. What is particularly nice about this, and a selling point to the students, is that if they later realize they need to add something or that they made a mistake and need to make changes, rather than having to redo the whole calculation, all they have to do is change the inputs and everything else updates instantly.
With our expenses totaled up, we can now begin figuring out how much this business is going to cost after each month by listing out the months in one column and the formula (which references the month number) in the second.
By using the spreadsheet, they can now quickly see how much the business costs after the first year, or any month before then, without having to redo the calculations.
All that is left at this point is to produce and share their graph for their business plan. To do this, I like to use a learning management software (LMS) system that allows students to create their own content, I have students edit a private wikisite to which they can embed their work directly. I prefer embedding to screenshots because it allows their tables and graphs to update on the web as they make edits to their original document; so I always have the most up-to-date version. Below are some images from two of my students final products.
