Drexel dragonThe Math ForumDonate to the Math Forum



Search All of the Math Forum:

Views expressed in these public forums are not endorsed by Drexel University or The Math Forum.


Math Forum » Discussions » Inactive » k12.ed.math

Topic: language of division
Replies: 9   Last Post: Jan 13, 2005 5:49 PM

Advanced Search

Back to Topic List Back to Topic List Jump to Tree View Jump to Tree View   Messages: [ Previous | Next ]
Kevin Karplus

Posts: 190
Registered: 12/6/04
Re: language of division
Posted: Jan 2, 2005 9:43 PM
  Click to see the message monospaced in plain text Plain Text   Click to reply to this topic Reply

In article <gjqgt0tetd3vkpkkoe3cb8dvncpemuahnv@4ax.com>, kalanamak wrote:
> The text I'm using on teaching children math forbids the use of "goes
> into" when talking about division. They say it is "meaningless". For the
> problem 427/62, they advise the child think aloud along the lines of
> 1) can 6 tens and 2 ones be subtracted from 4 tens and 2 ones? No. Can 6
> tens and 2 ones be subtracted from 4 hundreds and 2 tens? Yes. How many
> times? etc..
> OR
> 2) How many groups of 62 can I make out of 427 objects?
>
> Is this proper or farfetched? If the above is farfetched, is "goes into"
> still commonly used, or, if not, what is used?
> I am not clear from the text how the child goes about answering the 'how
> many times' or 'how many groups' question. Trial and error? Estimation
> and best guess first?


I don't know what elementary teachers now teach (mine tried hard to
avoid "goes into" 40 years ago, so it isn't a new prejudice).

Actually there is nothing inherently wrong with the "goes into" operator.
You can define it easily and unambiguously:
a "goes into" b =def b / a
It is not meaningless, just non-standard.

So far as I can tell, this operator is still used in speech (usually
pronounced "guzinta" around here), but not in writing---there is no
standard symbol for it.

The long-division algorithm has always suffered from the need to guess
how many times the divisor goes into the current part of the dividend.
If you guess low, you'll end up with a remainder that is too big, and
have to increment your guessed digit. If you guess high, you'll end
up with a negative remander and have to decrement your guessed digit.
Unfortunately, the algorithm is usually presented as if people always
guessed perfectly, losing a great apportunity to teach how to recover
from mistakes---a useful skill later on when dealing with more
complicated algorithms.




------------------------------------------------------------
Kevin Karplus karplus@soe.ucsc.edu http://www.soe.ucsc.edu/~karplus
Professor of Biomolecular Engineering, University of California, Santa Cruz
Undergraduate and Graduate Director, Bioinformatics
(Senior member, IEEE) (Board of Directors, ISCB starting Jan 2005)
life member (LAB, Adventure Cycling, American Youth Hostels)
Effective Cycling Instructor #218-ck (lapsed)
Affiliations for identification only.

--
submissions: post to k12.ed.math or e-mail to k12math@k12groups.org
private e-mail to the k12.ed.math moderator: kem-moderator@k12groups.org
newsgroup website: http://www.thinkspot.net/k12math/
newsgroup charter: http://www.thinkspot.net/k12math/charter.html



Point your RSS reader here for a feed of the latest messages in this topic.

[Privacy Policy] [Terms of Use]

© Drexel University 1994-2014. All Rights Reserved.
The Math Forum is a research and educational enterprise of the Drexel University School of Education.