# Ask Dr. Math Tour

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### Who Invented Decimals?

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From: RBECK@CCIT.ARIZONA.EDU
Date: Tue, 08 Nov 1994 13:23:01 -0700 (MST)
Subject: decimals

Hi. This is Tara, Erin, and David. We are fifth grade students and
one teacher. We would like to know who invented decimals.
Thanks.
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Date: Tue, 8 Nov 1994 16:38:58 +0900
From: mpatter1@cc.swarthmore.edu (Margaret Patterson)

Hi Tara, Erin, and David!

Thanks for writing to us.  This is an interesting question.

It is hard to point to exactly one person who invented decimals
since it is an idea that went through many notational changes and usage.
Decimals were used in ancient China, medieval Arabia, and Renaissance
Europe.  In the 1500's researchers and mathematicians were using some
form of decimals, but not until Simon Stevin of Bruges were they brought
to the common people.  He wanted to teach people, "how to perform with
an ease, unheard of, all computations necessary between men by integers
without fractions."  He dealt with tenths, hundredths, and thousandths not
as fractions such as 1   1     and  1, but rather as decimals.  He wrote them
differently, though.  He would write the power of ten assumed to be a divisor
after or above the each digit of the decimal, so the number 2.456 would be
written as

2 (0) 4(1) 5(2) 6(3)

where the parentheses indicate that a circle is drawn around the number, or

(0)   (1)   (2)   (3)
2     4     5     6

And he didn't use the words tenth, hundredth, etc.  He used "prime",
"second", "third", etc.

In 1616, the notation we use today first appeared in a book called
_Descriptio_ by John Napier (Scotland) using a decimal point to separate
the whole number part from the decimal number part. The next year he
proposed using a comma instead to separate the two parts.  Even today,
most parts of the world use the comma.