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Addition Facts

Date: Thu, 29 Jun 1995 00:23:23 +0300
From: Anonymous
Subject: adding 2 numbers


I'd like to understand the reason for the 'fact' that 2+2 = 4.
(It's not a joke, it really interests me to understand this.)

Date: 5 Jul 1995 10:15:17 -0400
From: Dr. Ethan
Subject: Re: adding 2 numbers

Well this problem is as much philosophical as it is mathematical.
The easiest (and somehow least satisfying) way to answer you is to say 
that it is definitional that 1+1 = 2 and that n + 1 = the next number bigger 
than n.

So 2+2 is 2+1+1, which is 3+1, which is 4.  The other way to think about it
is that + signifies the combining of two quantities, and the name for the
quantity that is the same size as 2 combined with itself is 4.

It really does come down to the "fact" that that is the definition.

If your question is more about why + was chosen to represent this combining
operation, write back and I will help you out.

Ethan Doctor On Call
Associated Topics:
Middle School Number Sense/About Numbers

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