The Math Forum

Search All of the Math Forum:

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

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

Notice: We are no longer accepting new posts, but the forums will continue to be readable.

Topic: Do you teach this subtraction algorithm?
Replies: 1   Last Post: Nov 19, 2004 12:42 AM

Advanced Search

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

Posts: 26
Registered: 12/13/04
Do you teach this subtraction algorithm?
Posted: Nov 16, 2004 5:26 PM
  Click to see the message monospaced in plain text Plain Text   Click to reply to this topic Reply

I think that this would be a great subtraction algorithm for those
whose attention wanders, because it is a "digit extraction" algorithm.

Example: 1776

By inspection, the answer is three figures.


Hundreds' digit: 7 minus 4 is 3, but since 76<92, write one less, that
is, 2.


Tens' digit: 7 minus 9... we are working mod 10, so make this 7+1=8.
As 6 is not less than 2, leave this 8 unchanged.


Units' digit: 6 minus 2 is 4. Result: 284.

I like this method because if your attention wanders, it matters
little, as each digit is calculated independently of all others.
Charming, huh?

submissions: post to k12.ed.math or e-mail to
private e-mail to the k12.ed.math moderator:
newsgroup website: <a href=""></a>
newsgroup charter: <a href=""></a>

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

[Privacy Policy] [Terms of Use]

© The Math Forum at NCTM 1994-2018. All Rights Reserved.