Erick Erickson has a Sad about Subtraction

Erick Erickson is sad.  Or mad.  I can't tell.  We'll just call it "smad" to make it easier.

Why is he smad?  Because the Common Core-based math book his third-grade daughter brought home contains four different ways to understand subtraction.

Here's the page out of her textbook that he's smad about:

Run!  It's maths!

The picture above is from my third grade daughter’s math book. This is the only page that explains that method for subtraction. There are, for the record, four ways to subtract that my third grader must learn.

This is the only page explaining that method. This is the only example. The very next page goes to arrays. The page after that goes to multiplication. This is it.

The traditional method of subtracting, borrowing and carrying numbers, is derisively called the “Granny Method.” The new method makes no freaking sense to either my third grader or my wife.