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 » sci.math.* » sci.math

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

Topic: Adding up license plate numbers
Replies: 5   Last Post: Jun 15, 2011 10:45 PM

Advanced Search

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

Posts: 1,412
Registered: 12/3/04
Re: Adding up license plate numbers
Posted: Jun 14, 2011 5:11 PM
  Click to see the message monospaced in plain text Plain Text   Click to reply to this topic Reply

In article
jbriggs444 <> wrote:

> On Jun 14, 8:04 am, Ashok <> wrote:
> > ....
> > When I am traveling by road, I frequently add up numbers on vehicle
> > license plates. For instance, if I see a license plate with the
> > numbers. EBD 2498, then I ignore the alphabets and add 2 + 4 + 9 + 8 =
> > 23 and then 2+3 = 5....

> The method that you have discovered is (or was) common knowledge
> before the advent of computers. Mathematically it is a computational
> trick to come up with the remainder of a number upon division by
> nine without having to actually do long division.
> It is (or was) one of the standard tools in a book keeper's bag
> of tricks when the books don't balance. Take the discrepancy,
> cast out nines and see if the result is zero. If so then you
> may have transposed digits somewhere.

I've nothing to add to that excellent answer; but the OP deserves to
be complimented on his mental arithmetic. Adding up numbers like that
is becoming a rare skill, especially if it's a background mental
activity while driving a car.

Ken Pledger.

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.