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Mathematics

 
Greenhorn
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Meiling and meimei divide $69 into 2 shares. 3/4 of Meiling's share is equal to 2/5 of Meimei's share. How much do each get?
 
author
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24 and 45.

Henry
 
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Henry is correct.

Let x equal Meiling's share, and y equal Meimei's share. Then...

x + y = 69
and
3x/4 = 2y/5

From the first equation, y = 69 - x. Substituting this into the second equation and solving for x...

3x/4 = 2(69 - x)/5
3x/4 = (138 - 2x)/5
15x/20 = (552 - 8x)/20
15x = 552 - 8x
15x + 8x = 552
23x = 552
x = 24

So y is 45.
 
Ranch Hand
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But what if Meiling and meimei's dad doesn't land them single penny?
[ November 30, 2008: Message edited by: Saurabh Pillai ]
 
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How is this mathematics? Its barely algebra.

I know, this is meaningful drivel, but if you want to talk about math, please take it at least to college level. Multidimensional calculus, number theory, topology, etc.
 
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Pat, are you trying to tell people what they can and can not post here? That would be somewhat out of line.

If you're interested in something else, why not post some of that yourself?
 
Pat Farrell
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Originally posted by Ulf Dittmer:
Pat, are you trying to tell people what they can and can not post here?



No, I'm just suggesting that calling algebra "mathematics" is like calling MS Basic from 1987 "professional programming"

When I saw the title of the thread, i went "oh boy, my favorite" but when I saw the content, I was discouraged.

Now its been 30+ years since I studied point set topology, and I've never had any use for it since, but it was my favorite course in Math, and my undergraduate degree is a BS in Math.
 
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Originally posted by Pat Farrell:
No, I'm just suggesting that calling algebra "mathematics" is like calling MS Basic from 1987 "professional programming"

Algebra is a branch of mathematics concerning the study of structure, relation, and quantity.

Wikepedia
 
Henry Wong
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No, I'm just suggesting that calling algebra "mathematics" is like calling MS Basic from 1987 "professional programming"



This is not really a good analogy. Knowledge of algebra is needed for many of the more advanced math subjects. I don't think that it will be possible to understand calculus, without a strong knowledge of algebra. Every professional mathematician, needs a strong knowledge of algebra.

On the other hand, I am pretty sure that there are many professional programmers, who never worked with the beginner's all purpose symbolic instruction code before...

Henry
 
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Simple mathematics is still mathematics. If it's not interesting, it's not that difficult to skip, right?
 
Marshal
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Originally posted by Pat Farrell:
No, I'm just suggesting that calling algebra "mathematics" is like calling MS Basic from 1987 "professional programming"

Yeah. I always get irritated by the phrase "Do the math" which almost always means "Do the elementary-school arithmetic". But then, I have a couple of math degrees myself so I have the same bias.
 
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Well... as useful as they are, finding the equilibrium points of non-linear differential equations or finding vector potentials in solenoidal fields are not my preferred pastime (no, I don't have fond memories of my calculus classes ).
 
Pat Farrell
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Originally posted by Gabriel Claramunt:non-linear differential equations


I hated differential equations. And I really didn't fall in love with calculus until the third time I took it. The first two were essentially "calculus for engineers" and aimed to teach the practical stuff. The third was more "third year calculus for math majors" and it was totally different. It was pure math, not something to support engineers.

The fact that an outfielder chasing a fly ball and runs to the right spot requires three dimensional differential equations being solved in real time, and that I love baseball, does not make me feel better about diff-eq.

The fourth time I took calculus, which was pure math calculus in N-dimensional space, was great fun.
 
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Originally posted by Pat Farrell:
The fact that an outfielder chasing a fly ball and runs to the right spot requires three dimensional differential equations being solved in real time


So this means that a DOG can do differential equations? and fish? After all, when I feed my fish, the food starts to drop in the water, and the fish are able to swim on an intercept course to eat the food.

I think that there is NO diff-eq being done by anyone in these situations. The ball players make a guess, then intake more data (by watching the ball) and continue to make a constant series of refinements to their guess as they watch the ball. They're VERY good at it from doing it a lot, but they are NOT doing diff-eq.
 
Java Cowboy
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I remember at university there was a janitor, one of the things he did was cleaning the blackboards.

He told us that sometimes a professor writes the whole blackboard full of mathematical symbols and formulas and at the end, in the lower right corner, it ends in: = 0

So, all those symbols and formulas were just a very elaborate way to write the number zero...
 
Pat Farrell
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Originally posted by fred rosenberger:
when I feed my fish, the food starts to drop in the water, and the fish are able to swim on an intercept course to eat the food.

I think that there is NO diff-eq being done by anyone in these situations. The ball players make a guess, then intake more data (by watching the ball) and continue to make a constant series of refinements to their guess as they watch the ball. They're VERY good at it from doing it a lot, but they are NOT doing diff-eq.



The fish doesn't have to time it exactly, the food will stay there and they can eat it instantly, or wait a few seconds. An outfielder has to catch the ball before it hits the ground.

I agree that they do it with estimates and feedback. But to model the path and speed of the outfielder as the angle of the ball's flight varies in what starts as a pure ballistic arc, but is really modified by wind gusts, etc. so that your computer model can show both the fielder's path and the ball's path, is sadly dif-eq.
 
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