Associated Topics || Dr. Math Home || Search Dr. Math

### 1 + 1 Doesn't Equal 2

```
Date: 06/04/98 at 20:22:58
From: Sara Locker
Subject: 1 + 1 doesn't = 2

It's a proven fact that 1 + 1 does not equal 2. What is the math
equation that proves this? My math teacher taught me this, but I
forget.

Sara
```

```
Date: 06/06/98 at 12:55:27
From: Doctor Peterson
Subject: Re: 1 + 1 doesn't = 2

Hi, Sara. There are actually lots of "proofs" like this, so I can't
tell which one you might have seen. Here's a classic example on the
Web that proves 1 = 2:

http://www.astro.virginia.edu/~eww6n/math/Fallacy.html

And here's a "proof" that 1 + 1 = 1 in our own archives:

http://mathforum.org/dr.math/problems/mayer9.4.97.html

and another that 2 = 1:

http://mathforum.org/dr.math/problems/wall10.3.97.html

Finally, here's a good discussion of several "proofs" like this:

http://www.math.toronto.edu/mathnet/falseProofs/

Of course, these aren't really proofs, because they all have some
error in them. What's important about these examples is that they show
ways in which you can make a mistake in using math if you aren't
careful enough. If you can understand where the error is, then you can
look for the same kinds of errors in your own work, whether it's a
proof for school or a calculation you make when you're designing a
bridge. It also explains why mathematicians and scientists don't
publish their results without first having others check them to make
sure there isn't some subtle error in their calculations.

-Doctor Peterson,  The Math Forum
```
Associated Topics:
Elementary Number Sense/About Numbers
Middle School Number Sense/About Numbers

Search the Dr. Math Library:

 Find items containing (put spaces between keywords):   Click only once for faster results: [ Choose "whole words" when searching for a word like age.] all keywords, in any order at least one, that exact phrase parts of words whole words

Submit your own question to Dr. Math
Math Forum Home || Math Library || Quick Reference || Math Forum Search

Ask Dr. MathTM
© 1994- The Math Forum at NCTM. All rights reserved.
http://mathforum.org/dr.math/