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Fundamental Math Failing

by JProffitt71
Tags: equivalence, linear equation, logic
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JProffitt71
#1
Oct31-11, 09:22 PM
P: 8
This should illicit a chuckle or perhaps despair in humanity.

The statement "One silver piece is equivalent to two copper pieces" is not equivalent to the equation "S = 2C" (Where S = silver and C = copper). I cannot for the life of me figure out why. I can work out every other way that to find the number of silver pieces you take the number of copper pieces and divide by two, and therefore it becomes "S = C/2", but I cannot look at the original statement and explain precisely why that makes sense.

I'm a physics major.
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disregardthat
#2
Oct31-11, 09:23 PM
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P: 1,807
What?
phinds
#3
Oct31-11, 09:28 PM
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[quote]
Quote Quote by JProffitt71 View Post
...

to find the number of silver coins you take the number of copper coins and divide by two
Also nonsense. you do not.
OK, I'm a doofus. Of course the number of silver coins is the the number of copper coins and divide by two. I was so distracted by your mistake in the first part that I let my mouth get ahead of my brain (not the first time).

JProffitt71
#4
Oct31-11, 09:40 PM
P: 8
Fundamental Math Failing

Quote Quote by phinds View Post
Look. Assign a copper coin the value of 50 cents and the silver coin the value of a dollar and examine your nonsensical statements
That makes perfect sense, and I am still perplexed. I suppose the graph is what I have an issue with. In my mind I expect it to show equivalent exchange at all points, and it does not. It actually shows the inverse.

Quote Quote by disregardthat View Post
What?
This is what happens when I do not get enough sleep it seems.
Citan Uzuki
#5
Oct31-11, 09:57 PM
P: 274
The problem is that you're using the same symbol to mean two different things. In the equation S=2C, S and C stand for the value of the silver and copper pieces. But in the equation S=C/2, S and C stand for the number of silver and copper pieces that you have (assuming that currency can be exchanged at will). Since the two equations are modeling different things, it is no surprise that the equations are different.
JProffitt71
#6
Oct31-11, 10:03 PM
P: 8
Citan Uzuki, thank you very much. Order has been restored. I am quite a fool.


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