I got a nifty gift yesterday from one of my tutoring clients. It’s a pencil case. But not just any pencil case. It’s made of one giant continuous zipper. Check out my Zipit Monster Pouch:

As I was enjoying it, I began wondering a couple of things:

- What would it look like opened up?
- How long would it be opened up?

### There are two ways to solve the problem.

The temptation is to just unzip the thing and look. And indeed, that would be one way to answer my questions.

But if something like this hits your math class, consider approaching it “the hard way.”

What we know:

- Totally flat, the monster is 8.75 inches long and 4 inches wide.
- The diagonal from corner to corner is 9 inches.
- On each side, you can count 7 diagonals of zipper.

What we might need to know:

- What’s the angle of the diagonals?
- How does the zipper wrap around?

What might be fun to figure out:

- If I wanted a coin purse like this, how much zipper would I need?
- If I wanted a shoulder bag like this, how much zipper would I need?

### Can you use it as a lesson?

If you propose the questions to the class, can you use it as a Project Based Learning activity? There’s some serious geometry going on here!

Share your thoughts in the comments!

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