Session 3, Part C:
Function Machines

In This Part: About Function Machines | Running a Function Machine | Function Machines and Undoing

Take a look at this algorithm (let's call it Algorithm C):

 • Pick a number (that's the input) • Multiply it by 2 • Add 3 to the answer • Multiply that answer by 10 • Add 6 • Finally, divide by 2

Draw a function machine network or print out a copy of the function machine network below to help you answer Problems C1 - C5.

Problem C1

If the input to Algorithm C is 3, what is the output?

 Problem C2 If the output to Algorithm C is 88, can you determine what the input was? How did you do it?

 Problem C3 Use the Interactive Activity to build Algorithm D, which undoes Algorithm C. How would this help with Problem C2?

 Problem C4 Imagine that Algorithm C and Algorithm D are connected to form one large network. What would happen to a number used as an input in this network? Think about it for a few minutes, and try a few numbers if you need to. Connecting the two networks gets you back to your original number. Going through all these steps turns out to be a complicated way of doing nothing to a number!

 Problem C5 See if you can use the function machines network to produce the following outputs: 59, 216, 15625, 7280, 0.12345. As an additional challenge, use the fewest possible machines to do so.

 Session 3: Index | Notes | Solutions | Video