[MD] 2 + 2 = 5?

[Ron Kulp]

The statement is, "2 + 2 = 5 for very large values of 2." It's a joke
about rounding and estimating. 
For instance, suppose you have your calculator set to round all numbers
to integers (no decimal places) 
and the problem you're actually computing is 2.48 + 2.47. The calculator
will automatically round, 
so when you punch 2.48 and ENTER, it will show up on the screen as 2.
When you punch in the 
2.47 and ENTER, it will also show up on the screen as 2. Then when you
add, the sum 4.95 will 
be rounded to 5. Hence, 2 + 2 = 5 if the value of 2 is large enough.

It's a joke ... but a joke with a somewhat serious point. All
measurements in the real world 
(as opposed to the esoteric whirled of mathematics) are estimates;
they're always rounded to 
something. There's no such thing as absolute precision. So rounding must
come into play 
sometime or other, and the joke about 2 + 2 = 5 if 2 is large enough, is
a reminder about the 
way that estimation errors compound.