In a simple table to subtract two negative numbers ( -6 from -3) my
formual is =SUM(S6-S7) . Excell gives me the answer 3. The answer is
actually -3. What's wrong with my formula? The answer must say -3 for
graphing purposes with the data I'm using. Thank you, Jeff.


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elyandco
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hey man you should try S7-S6 then you will find the answer -3.



tell me its working or not.


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dalipsinghbisht
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Right...I was just in the process of realizing what I had done, and that
mathmatically, Excell gave the correct answer for what I asked it to
do....and as you say by reversing the problem, I will get the -3.

I'm a piano tuner...I tune with a device that can measure any given
note, so that before I tune a piano, I'll know how far off it is from
where I want it to be before I start. If I can develope a simple table
and insert values for each octave of the scale, first inserting what
that note should be tuned at, and then measuring that note and
inserting where it is before the tuning, then with the differences
between the two data for each note I could get a graphic
representation, a visual to look at of the existing scale before it's
tuned. This is actually very important to know, and determines how much
"stretch" we must pull on each string during tuning...(tons more on this
if your interested).

The problem is, that in some cases, the result does not represent the
reality.

Thanks for your help...I've got to try and wrap my head around what I
want to do here...I'm not a math type, just thought it would be cool to
have a graphic rep of each tuning I do, would be good for future
comparisons cuz I do a lot of institutional tunings...same pianos over
and over. May not be worth the trouble.


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elyandco
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elyandco wrote:
In a simple table to subtract two negative numbers ( -6 from -3)
my formual is =SUM(S6-S7) . Excell gives me the answer 3.
The answer is actually -3. What's wrong with my formula? The
answer must say -3 for graphing purposes with the data I'm using.

If you subtract -6 "from" -3, i.e. -3 - (-6), the correct answer is
indeed 3.
If you intend to subtract -3 "from" -6, i.e. -6 - (-3), then say that,
and
write your formula accordingly. I presume that S6 contains -3 and S7
contains -6. If yours is the latter intent, write S7-S6.

But always remember GIGO -- "garbage in, garbage out". If you
manipulate the arithmetic to give the expected result, that does not
necessarily give the correct result. Understand your math problem,
and do the correct arithmetic. If the result surprises you, be
prepared
to accept the fact that your expectation was wrong, perhaps.

PS: You do not have to use SUM() in this context. It serves no useful
purpose here.