[AT] Having battery problems--so how to fix?

[Larry D. Goss]

20C = 68F.  That's been drilled into my head so much because of photo
processing that I'll never forget it.  Plugging those known numbers into
your "by guess and by gosh" equations gives:

C/2 + 30 = F
20/2 + 30 = F
10 + 30 = F
40 = F or 20C = 40F

and 

(F-30) * 2 = C
(68-30) * 2 = C
38 * 2 = C
86 = C or 68F = 86C

86C is hot enough to cook an egg, and 40F is a pretty chilly day.  I
don't think you can claim that big of a difference as a "margin of
error."

I'm reminded of the old riddle about which clock is right most often?
One that gains a few seconds per day, or one that doesn't run at all?

I wonder if the Farmer's Almanac has a fast estimator for this
conversion?

Larry



> Ok let me do this right.
>
> ((C/5)*9)+32=F
>
> ((F-32)/9)*5=C

If you need correct numbers the above is correct.  If you just need a
close 
enough number so you know what is going on, the following is close
enough for 
most uses:

C/2 + 30 = F

(F-30) * 2 = C

Much easier - I suspect most of us can do my version in our heads (and
we 
might even be able to remember it).  It won't be right of course, so
beware 
when you present answers from my version.  Some people do not understand

margin of error, and thus cannot accept anything with such a thing, (In
many 
cases my version is in fact 100% correct because the margin of the error
on 
your thermometer is greater than the errors my version would add).
There 
are also cases where tiny differences matter, so don't even think about
my 
version for science labs.