Functions can be a hard concept to teach to primary and secondary students! Math Is Fun gives as good of a review as anyone. One of the hardest concepts for students to grasp in when a function is really a function and when it isn’t. If we are lucky enough to have a graph then we may simply use the vertical line test but normally this is not the case, so, let me offer an analogy

__Using text messaging for our example here are our definitions using inputs and outputs.__

Function: Cell Phone

Input: Cell phone numbers in our address (a)

Output: Sent text messages (TM)

Our Function is thus

TM = f(a)

Text massages are a function of what address we input.

Now we have a platform to teach our function concept. For additional questions, download the worksheet titled What is A Function in the math downloads section

## 2 comments:

Where is the worksheet?

Otherwise, I like the idea of the phones as a model. But doesn't the text message change so that the same input cell#, has different outputs? Or is that your point?

If the output is the recipient, then it's a function.

Hey John, The worksheet is titled "When is a Function" and is in the Math Downloads section to the bottom right (if you can't find it, send me an e-mail and"ill mail it to you).

You're right that the concept can get slightly tricky to teach. The way i'm thinking is that you may send the same message to multiple people (and it's still a function), but you cannot send a message to input mom and it be received by dad. If you think about listings in your phonebook as the input and the receiver as the output I think it will work for an analogy. Let me know how it goes :)

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