 Mildred had been experimenting with black eyeliner and mauve lipstick. She sat down and asked me what I thought. I was smart enough to know not to answer a trick question like that! Instead, I asked her what she'd been learning in math class. "We're learning about evaluating expressions and stuff like that" she replied. The mauve lipstick didn't appear to be affecting her ability to speak, although the dog was keeping her distance. I took the opportunity to introduce Mildred to functions and the Mystery Function Box. "Let's look at an example of a function. I won't tell you what the Mystery Box is doing, but you can experiment with different numbers, to try to find out what changes the box is making to your number". "The box is called a function. Every function does something different to a number". "Here are some more examples of some simple functions": 'Double It' This function doubles a number. For example, it changes 5 into 10. 'Triple and Add One' This function multiplies a number by three, and then adds 1. For example, it changes 5 into 16. 'Halve It' This function finds half of the given number. For example, it changes -8 into -4. "Functions can be described in mathematical terms, to make them easier to write. The number you want to change is usually represented by x Here are the same three examples from above, written in mathematical notation": 2x 'Double the number' This function doubles a number. For example, if x is 5, the result is 2 times 5 = 10. 3 x + 1 'Triple the number and add one' This function triples a number and adds 1. For example, if x is 10, the result is 3 times 10 plus 1 = 31. x/2 'Halve the number' This function finds half of the number. For example, if x is 6, the result is 6 divided by 2 = 3. "Try another mystery function. Here are some numbers, listed on the left, and what they got turned into, on the right".
Mildred wanted to try one more, so I gave her this example:
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