This week’s Math Goggles challenge is a perfect excuse to go out and buy a dozen of freshly baked bagels. At least it was for me. (If you are not sure what is a Math Goggles challenge, read about it here). So the question is what do you get when you slice a bagel.

The answer depends on how you slice it. That’s one reason you need several bagels. **Begin** by cutting the first bagel horizontally. What will the cross section look like when you finish slicing? Easy, right?

**Next bagel!** Instead of making a horizontal cut, slice this one in half vertically. Can you predict what the cross section will look like this time? Still easy-peasy! (And now you know the correct answer next time you see this little puzzle floating around on Facebook)

Time for **bagel #3**, inspired by James Tanton. Can you slice it in such a way (different from the first two) that the cross section will show two circles? Hint: choose your best-looking (most torus-like) bagel for this one.

The **forth bage**l can be cut into a trefoil knot which is super easy to do, but you sacrifice the ability to toast your bagel before putting cream cheese on, or rather in, it.

Four down, **eight more to go**. Time for the big one, George Hart’s interlocking bagel halves puzzle. I made a mistake of putting half my bagels into the freezer, so by the time I attempted this problem, I only had 2 bagels left. And I didn’t want to draw on any of them with a Sharpie. Let’s just say that I learned a few valuable lessons in the process and ended up with a failed, but perfectly edible experiment.

So, sharpen your knife, get out a tub of cream cheese, and keep your eyes open for math!

Posted in Grow

And a related problem with a cube:

http://fivetriangles.blogspot.com/2012/04/basic-geometric-shapes.html