Common Core Subtraction

Oct 7, 2014 by

Andy Kiersz –

The Common Core math standards are a topic of hot controversy, especially on the right. The Daily Signal, a news and commentary site started by the Heritage Foundation, recently featured this picture from Red State editor-in-chief Erick Erickson’s blog, showing a page from Erickson’s daughter’s third-grade math textbook:

commoncoreErick Erickson

The above shows a way of doing subtraction that’s probably different from what you learned in school. Rather than the basic “carry-the-1” approach, students are taught to see subtraction as a way of establishing the distance between two numbers. And the easiest way to do that is to establish the distance between various signposts. So the way to subtract 38 from 325 involves establishing the difference between 38 and 40 (2), 40 and 100 (60), 100 and 300 (200), and 300 and 325 (25). Adding 2 + 60 +200 + 25 gives you the answer: 287.

Anyway, alternative methods like this one, or the “box multiplication” method we’ve looked at before, have raised a stir among some parents and conservative commenters. The Daily Signal’s Kelsey Harris notes that “students must take about six steps (at minimum, depending how you count) to subtract just two numbers” using this method. Erick Erickson wrote that this method “makes no freaking sense to either my third grader or my wife.”

via Common Core Subtraction – Business Insider.

Print Friendly, PDF & Email

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.