Use and Meaning of 'And' in Naming Decimals

Date: 12/01/2004 at 20:11:12
From: Emily
Subject: May you please tell me what the word "and" means in math?

Dear Dr. Math,

Can you please tell me what the word "and" means in the word form of a
decimal number?  I don't normally see it when it is not used for math!

Date: 12/01/2004 at 23:21:59
From: Doctor Peterson
Subject: Re: May you please tell me what the word "and" means in math?

Hi, Emily.

You're probably thinking of the fact that, at least when we read a
number the way teachers commonly insist, "and" is used only between
the whole number and the fractional part.  For example, we would say
"one hundred fifty-two" for "152", but "one AND fifty-two hundredths"
for "1.52".  Of course, in real life people don't always follow that
rule; but it does make sense if you want to be careful in your
speaking.  But the "and" there really doesn't have any different
meaning there than it usually does, to connect two things together,
meaning more or less the same as "plus".  What's more important is
that by only using it at the decimal point, when it is NOT used you
know there is NOT a decimal point there!

The value of using "and" carefully shows up mostly in fractions.  Note
the distinction here:

  one hundred and three hundredths = 100 3/100 = 100.03
  -----------     ----------------

  one hundred three hundredths = 103/100 = 1.03
  -----------------

Also,

  one hundred three-hundredths = 100/300 = 1/3 !
              ----------------

See this page:

  Saying Numbers Out Loud
    http://mathforum.org/library/drmath/view/57225.html 

This page deals with the related issue of hyphens:

  Place Value and Similar Numbers
    http://mathforum.org/library/drmath/view/63862.html 

If you have any further questions, feel free to write back.


- Doctor Peterson, The Math Forum
  http://mathforum.org/dr.math/