Number sense and harder stuff

Posted on March 8, 2016

Yesterday I was working with a student who was doing the “integer addition” activity.   For the problem “9 + -5” the student would write 9 letter Bs and 5 letter Rs.

This is an extension of “adding with chips” such as is shown here: https://www.youtube.com/watch?v=7x7H09-Cca4   (I’m liking this tho’ I just posted it ’cause it was the first one).   An even crazier version of this is Integer Eyes.

Usually the students just write the letters in a row.  This student neatly wrote them in multiple rows.

At first I thought that the student had teh number sense to be doing some grouping but… the numbers in each row seemed to be random.   They’d been shown that R & B added up to zero, & “zapped” each other (not as a “trick” but as a model)… but at first she was treating all the letters the same so if it were -3 + -4 the answer was -1.

She could get it on the number line, once she learned not to plop both numbers on the number line, but to pay attention to direction and change 😉

I think doing things in both formats was a benefit, though, because at the beginning of the exercise she was excising R… B    R… B, one at a time (once she knew to check to make sure they weren’t the same letter).     I suggested that she put the same number in a row (I couldn’t figure out a pattern; anywhere from 3-5 would go in a row and then she’d start over, and it would be different for the R’s and the B’s in the same problem).

The idea that she could just “cross out” five B’s and then 5 R’s … and then continue from there… was news.   This is consistent with math ed development stages…

… and we can work with that, *without* going back to elementary math.   Context is everything…