walkitout (walkitout) wrote,
walkitout
walkitout

This Might Explain a Lot About Conservatives

http://www.businessinsider.com/common-core-subtraction-2014-10

Conservatives don't like Common Core. That's not news. Red State is a blog. Also not news. Red State's editor in chief Erickson says his wife and his 3rd grader can't understand subtraction. Specifically, the counting up method of subtraction, an alternative method of subtracting that anyone who does mental arithmetic does automatically, and which is included in Common Core textbooks and has some nice side effects like helping people internalize quantity and quantitative relationships, rather than just relying blindly on a sequence of nonsensical steps the way traditional algorithmic arithmetic tends to encourage people to do.

"Erick Erickson wrote that this method "makes no freaking sense to either my third grader or my wife.""

If conservatives in general are innumerate, it might or might not be news, but it would be a very powerful explanation for some of their positions (not their terrible morals, but why they keep getting suckered by foolishness about the effects of tax cuts).

I had never seen (to the best of my recollection) this sequence of steps before, but it captures a lot of the rounding up/rounding down and then adding back in that I do mentally doing arithmetic -- I can't make the standard method work consistently without something to write on, but this one I can hold in my head. It took me a minute to understand the sequence they laid out, because it is a little different from what I do, but the spirit is recognizable. Anyone who has a lot of trouble figuring out this way of subtracting probably hasn't really understood subtraction, other than as a rote sequence of steps.

FWIW, I expect that anyone who _does_ have trouble with this might find that after a half dozen to fifty worksheets with a hundred of these problems on them will help them with their difficulties. It might even help them better understand quantity relationships as well, contributing to their overall numeracy.

ETA: the sequence in my head goes like this. 325 - 38 = ?

320 - 40 = 280
280 + 5 = 285
285 + 2 = 287

So I drop the trailing digits initially, rounding down on the larger number and up on the lower number, so I only have to add when I put them back in. Then I subtract the now manageable single digit from double digit (32 - 4 = 28) and put the zero back on. Then I add back the dropped digits.
Tags: education, politics
Subscribe
  • Post a new comment

    Error

    default userpic

    Your reply will be screened

    Your IP address will be recorded 

    When you submit the form an invisible reCAPTCHA check will be performed.
    You must follow the Privacy Policy and Google Terms of use.
  • 6 comments