@sozobe,
I haven't tried it yet, not being in the mood last night when I read the question (too much like some of my old work tasks, fer heven sakes) and by this morning just amused by all the different answers.
I decided I'd look at it this afternoon when I got back from the grocery store, but still haven't applied my reluctant self. Still, on the way to the store I thought how I'd do it, and it mirrors what I now see Sozlet came up with. I still haven't applied myself though, what with my reluctance factor (impedance?).
I did think it would be fun to grab my 1/4" grid paper and play with it as 1/4" = 9" or 0.75'. Perhaps even color the squares. We'll see. (I might rather clean the refrigerator.)
I do think the question is tricky for fourth grade. Even the black and white square thing in itself seems too tricky for that level, confusing to many.
As a first math homework thing, it seems a knockout punch.
It reminds me a little of a class I had at university in Serology, which had a lot of beginning immunology matters rolled into the lectures. There were three of us at the head of the class grades all the way through, including our experiments, and including A's in the final, except that we all missed, for different reasons, the mid term.
Me, I remember I was busy throwing up from the flu.
So, the instructor gave us a makeup test, a single question about how would we devise an experiment re (whatever, I forget). All three of us f'ked it up completely, what?, so we got F's on the midterm and C's in Serology. I remember thinking it was a tricky question directed at us three in particular as a challenge, whereas the rest of the class got a regular one hour multi question ordinary test.
Boo hoo, except that memory is long, and Mo's math question triggered that memory.
holey schmoley... 
