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Author Topic: Question for math majors...  (Read 581 times)

Offline Gunthr

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Question for math majors...
« on: July 08, 2003, 08:53:50 AM »
What is the change, expressed as a percent, going from 3 to zero?
Please explain why.

Also, what is the change going from zero to 3 expressed as a percent, and why?

I'm trying to explain why going from 3 murders in 2002 to zero murders in 2003 is being spit out by the excel program as a (-100%) change.

Yet going the other way from zero to 3 is a (+300% change)

If this is correct, how do I explain this?
« Last Edit: July 08, 2003, 08:58:39 AM by Gunthr »
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Offline ra

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Question for math majors...
« Reply #1 on: July 08, 2003, 09:24:57 AM »
Quote
I'm trying to explain why going from 3 murders in 2002 to zero murders in 2003 is being spit out by the excel program as a (-100%) change.

This makes sense, 100% of the annual murders stopped.
Quote
Yet going the other way from zero to 3 is a (+300% change)

This doesn't make sense, using zero as a starting point you get infinity.  Excel probably substitutes one for zero, like the AH K/D calculation.
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Offline zonta123

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Question for math majors...
« Reply #2 on: July 08, 2003, 09:56:52 AM »
im not a math major. however basic math suggests:

going from 3 to 0 is -100% because 100% of 3 is 3, and -100% would mean deducting all of it so you get 0. Same is true for any number to 0 (99129192129 to 0 is still -100%)

yet 0 to 3 is NOT 300%.  I don't see how you compute it.  The way to compute change is (x-y)/x which is what you used for computing 3 to 0.

if you apply that formula to 0 to 3, it is incomputable since you cannot divide a number by 0.   Answer would be: change from 0 to 3 cannot be expressed in %.

messing with zeros and 1s always play tricks on ya ;)

if it is indeed possible to express 0 to 3 in % I would love for someone to explain how.

regards
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Offline zonta123

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Question for math majors...
« Reply #3 on: July 08, 2003, 10:00:48 AM »
Quote
Originally posted by ra
........ Excel probably substitutes one for zero, like the AH K/D calculation.


1 to 3 is 200% so I dont think excel substitues 1 for 0. It should give an error. Gonna check and make sure tho..
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Offline ra

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Question for math majors...
« Reply #4 on: July 08, 2003, 10:20:56 AM »
Quote
Originally posted by zonta123
1 to 3 is 200% so I dont think excel substitues 1 for 0. It should give an error. Gonna check and make sure tho..

I didn't say it was right, but that's probably what happens:

(x - y) / x -->  (3 - 0) / 0     becomes   (3 - 0) / 1 = 300%

If the change was from 3 to 1 it would be (3 - 1) / 1 = 200%
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Offline Syzygyone

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Question for math majors...
« Reply #5 on: July 08, 2003, 10:28:30 AM »
Quote
Originally posted by zonta123
messing with zeros and 1s always play tricks on ya ;)



Quote from "Bill Gates - The Early Days":D
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Offline Gunthr

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Question for math majors...
« Reply #6 on: July 08, 2003, 10:33:02 AM »
From Ask Jeeves

Calculators have the following method for figuring percent change hard wired into them:

"Divide the change by the starting value, and multiply the resulting fraction by 100."

So, for a change of 3 to zero expressed as a percent:

Change = 3
Starting value = 3
3 divided by 3 = 1
1 x 100 = 100
= (minus 100 % change)
So that explains why excel spits out (-100%)

HOWEVER, if my excel program is using that method, as far as I can tell, the change from 0 to 3 expressed as a percent would be:
Change = 3
Starting value = zero
3 divided by zero = 3/0
3/0 = zero !!!!

But excel shows (+ 300%) change going from zero to 3 when I use the above method. I'm confused. Did I do something wrong?
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Offline midnight Target

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Question for math majors...
« Reply #7 on: July 08, 2003, 10:33:19 AM »
I plugged that into Excel and got this:

3   0   100.00%
0   3   0.00%
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Offline Gunthr

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Question for math majors...
« Reply #8 on: July 08, 2003, 11:28:03 AM »
Thats interesting, MT. Those numbers make sense, but differ from what I get from my Excel program.

Now I'm wondering, not being very familure with Excel, is it possible that someone plugged in parameters or a certain formula into MY Excel program that would give me:

0 3 300% ??? - because that is what I get (300%) percent change going from zero to 3 in my excel program...
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Offline midnight Target

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« Reply #9 on: July 08, 2003, 11:46:03 AM »
What is the formula in the cell showing 300%?
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Offline Gunthr

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Question for math majors...
« Reply #10 on: July 08, 2003, 11:54:16 AM »
I'm away from the office now... will check a little later...
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Offline Gunthr

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Question for math majors...
« Reply #11 on: July 08, 2003, 01:35:32 PM »
MT, I didn't know what you meant by "formula for that cell" but I got somebody to show me. The formula for that cell is:

=IF (D10>0,((C10/D10)-1)*1,C10*1)

It's obvious that that is why I get a 300% change going from zero incidents to 3 incidents, while you get zero % change..

Boy I'll be glad when the secretary gets back from vacation - she knows about all this stuff. Thanks for the tip... gave me a chance to look smart in front of my boss :p
« Last Edit: July 08, 2003, 01:38:27 PM by Gunthr »
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Offline rpm

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Question for math majors...
« Reply #12 on: July 08, 2003, 02:28:27 PM »
Quote
Originally posted by Gunthr
[B The formula for that cell is: =IF (D10>0,((C10/D10)-1)*1,C10*1)
[/B]


STOP IT! You are making my brain smoke! AAAAAAAAAAAAAAAARRRRRRRRGGGGG GGGGGGG!:eek:
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Offline midnight Target

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Question for math majors...
« Reply #13 on: July 08, 2003, 05:47:50 PM »
Quote
Originally posted by Gunthr
MT, I didn't know what you meant by "formula for that cell" but I got somebody to show me. The formula for that cell is:

=IF (D10>0,((C10/D10)-1)*1,C10*1)

It's obvious that that is why I get a 300% change going from zero incidents to 3 incidents, while you get zero % change..

Boy I'll be glad when the secretary gets back from vacation - she knows about all this stuff. Thanks for the tip... gave me a chance to look smart in front of my boss :p


NP bud.

(If the value of 3 is in cell C10 then the cell will return '3' as the result and since the cell is formatted as a percentage it will look like 300%)
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Offline funkedup

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Question for math majors...
« Reply #14 on: July 08, 2003, 05:53:30 PM »
NERRRRRRRRRRRRRRRRRRDS :)
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