# The Math Wizard

Okay, one more shout out.

My colleague Japheth Wood (News from the Math Wizard), with whom I’m delighted to be co-teaching a class for preservice teachers, is an awesome problem composer. He’s also been dipping into the sea of math and math ed blogging, one toe at a time. He’s finally got one whole foot in:

Check it.

In particular, check out that image.

Don’t move past it to the text (mine or Japheth’s) until you’ve sat with it long enough to absorb everything. If you find yourself with a mathematical question, don’t move on till you’ve tried to answer it.

Seriously; stop reading and go look.

There’s a lot of difference, pedagogically and content-wise, between this image and Dan’s boat-in-the-river video but there’s something very important and very exciting in common. Both manage to ask a very specific and mathematically rich question without whispering a single word. I think the natural current could be strengthened a bit by putting little venus flytraps on top of the square numbers, but that’s the only improvement I can think of.

So, questions for you:

a) What question, if any, does that image leave you with? (Am I right that there is a natural question you can’t help but have once you’ve absorbed the image?)
b) What are the features of the image that lead to the question? Given a mathematical question, how do we go about turning it into a wordless image that asks it?

FOLLOWUP (10/1/10):

Japheth and I passed out slips of paper to our class of preservice math teachers a week ago. On the slips were either Japheth’s original image, or tieandjeans’ modification. We asked them to write down a mathematical question that the paper provoked, and then try to answer it. We didn’t give them a ton of time. (Less than 10 min.) Interestingly, while I thought the sense of danger in the modification would make the gravitational pull toward our intended question (will the grasshopper manage to avoid all the squares?) greater, our students’ knowledge of Super Mario Bros was a distraction, because the up/down motion of the plants, and the question of Mario’s specific trajectory, became relevant considerations. (You can see below that one group, perhaps reading what we were going for, explicitly ruled out those considerations.) So I think the students that got the original grasshopper image actually gravitated toward the intended question more predictably. I still think the sense of danger would help, but maybe we just keep the grasshopper and add venus flytraps that appear static and aren’t close to the trajectory?

Anyway, here’s what they came up with. As you can see, for all of the above, the natural current is still pretty strong.

Grasshopper / Mario Problems

—=—=—=—=—=—=—=—=—=—=—=—

If the placement of fly traps continues, and Mario times his jumps so the trajectory never hits the plant, will he ever land on a fly trap and die?

$a^2 = 4n + 2$. No.

—=—=—=—=—=—=—=—=—=—=—=—

Does Jiminy land on a box?

$4k+2$, $k\in\{0,1,2,\ldots\}$
$k^2 = 4k+2$
$k^2 - 4k - 2=0$ —> $k = 2 \pm 2\sqrt{6}$

—=—=—=—=—=—=—=—=—=—=—=—

When does Mario’s jump not clear the venus fly trap?

—=—=—=—=—=—=—=—=—=—=—=—

Will the grasshopper land on one of the empty boxes (perfect squares)?

—=—=—=—=—=—=—=—=—=—=—=—

Hopping by 4. What is the mathematical formula to determine where Mario lands?

Mario will never land on a perfect square.

—=—=—=—=—=—=—=—=—=—=—=—

How many times will the grasshopper land between consecutive perfect squares?

For # between $(n-1)^2$, $n^2$, if odd then $(n-1)/2$, if even then $n/2$.

Will he ever land on a perfect square?

—=—=—=—=—=—=—=—=—=—=—=—

Can the grasshopper keep jumping without hitting the black box? If no, then when will he hit the black box?

—=—=—=—=—=—=—=—=—=—=—=—

Patterns
Grey boxes increase by +4
Black boxes increase by consecutive odd #s, +3, +5, +7, +9

Questions
Do you notice a pattern between the grey boxes? How about the black? Can you predict what # Mario will land on next?

The next plant will appear at 36. Mario will land at 26, then 30.

When will Mario land on a flower (perfect square)?

—=—=—=—=—=—=—=—=—=—=—=—

$2+4y = n^2$

Will Mario die and when?

—=—=—=—=—=—=—=—=—=—=—=—

When will Mario land on a plant?

Can he change the size of his jumps and still ensure he will not land on a plant?

—=—=—=—=—=—=—=—=—=—=—=—

Will the grasshopper ever land on a black square?

Can (4n-2) be a perfect square?

—=—=—=—=—=—=—=—=—=—=—=—

Will the grasshopper land on a boxed number (i.e. a perfect square)?

$4n - 2 = (y^2 + 0^2)$
Sum of squares must be a multiple of 4 or odd.
No.

(Ed. note: they’re misquoting a result they found the previous week. The result was about the difference of squares.)

—=—=—=—=—=—=—=—=—=—=—=—

## 7 thoughts on “The Math Wizard”

1. tieandjeans says:

OK, that’s just fantastic. I was late to a meeting becuase I had to show it to the kids in aftercare, who all jumped to the right question and started to sketch out their solutions.

When I got home, I had to tweak it just a bit for my middle school students. Of all the places I’ve abused Mario pixel art, this may be my favorite.

Thanks for passing on a great problem!

2. ben wheeler says:

wow, i really had to push myself to stick with the image and think about what it was trying to say. it’s funny how ingrained the instinct to want explanations is. i actually really needed your second time linking to the image to go back and spend time with it.

and i totally agree about the venus fly traps.

3. @ tieandjeans – awesome. Just what I had in mind.

@ Ben – what up!

4. p.s. tieandjeans – if you use it with the middle schoolers, tell us what happens!

5. I didn’t get it until I read “venus flytraps.” ItslateImtired.

6. Thanks Ben, for passing on my presentation of that problem. As I mentioned, the concept came to me while helping a student understand a tricky notion.

@ tieandjeans – I love what you’ve done with it. Great job! I’m also eager to hear how the middle schoolers engage with it.

7. Guy Srinivasan says:

Odd, I didn’t think of whether it’d land on a square *at all* until I read on. I did think of two mathematical questions, and answered them, before reading on:

a) The grasshopper’s always within 2 of a square. Why? Oh, it’s not, not even in the picture.
b) The grasshopper jumps once between the first two squares, then once, then twice, then twice. Does this continue? 3x 3x 4x 4x etc? What’s (x+1)^2-x^2? It’s 2x+1, so the gap goes up by 2 each time, and by 4 every second time, and each jump is 4 wide, so yeah it continues at least approximately.

After those two I thought “what other question…? eh, dunno, I know what it looks like in the long run so I’m probably done, let’s go back and read on”.