I know the ruler seems a bit overkill for a simple subject like
adding positives and negatives, but I teach 11th grade in Boston
and it’s the biggest stumbling block for even my students taking
my advanced algebra class. The problem is that kids are taught a
“noun-verb” way of solving problems like “-12 + 7″. They are
told to find -12 (noun, static number) and count up 7 spaces
(verb, movement) to the right to see what number they land on.
This is fine in a classroom with a number line taped to the
desk, but it doesn’t teach the kids how to think about the
numbers and a lot of kids will get this problem, and ones like
it, wrong. It only gets worse with “x + 12 = 7 (solve for x)” or
“y + 12x = 7x + 3 (solve for y)”. It’s the same problem over and
over again, just disguised. The problem with the number line and
the “noun-verb” way of solving is that it’s not the way we
think. It’s not even the way we are taught in school to solve
these problems. In the Boston 7th grade curriculum is a book
called “Accentuate th