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FC/OT: This is why LionJim stays off Twitter....

PEMDAS is currently tending in the U.S.:

"The concept of mathematics being purely objective is unequivocally false, and teaching it is even much less so," the document for the "Equitable Math" toolkit states. "Upholding the idea that there are always right and wrong answers perpetuate objectivity as well as fear of open conflict.”
 
PEMDAS is currently tending in the U.S.:


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Ronald Gabriel Palillo (April 2, 1949 – August 14, 2012) was an American actor and teacher.[3][4] He was best known for his role as the endearingly dim-witted character Arnold Horshack on the ABC sitcom Welcome Back, Kotter (1975–1979).[5][6]

One of the great series i watched while in high school... Arnold Horshack, ...truly sorry I outlived you. Fun series, one that I'll always remember.
 
usually I can see how a wrong answer could be made, but how does that person come up with 7?
I’m getting 9.
P = 1 + 2 = 3
E = nothing
M/D = work left to right as the P is dropped.

6 /2(1 + 2)
6/2 * 3
3 * 3
9

@LionJim can you check my work please?

OL
I can vouch ... you got it right!

One reason I don't subscribe to the acronym PEDMAS is that many think you do division before multiplication and addition before subtraction while the correct thinking is you do division and multiplication at the same level working left to right, same for addition and subtraction.
 
As is always the case with MATHS. o_O , the answer is subjective and therefore open to interpretation.
 
The reasoning at the root of performing multiplication OR division left to right regardless whether the operation in a given expression is division before multiplication is that division is defined as “multiplication“ by the reciprocal or inverse of the
divisor. This is how I taught PEMDAS to high school students for 40 years.
As shown by both OhioLion above, the answer is. 9.
 
The truth is that many elementary and middle school math teachers teach the order of operations incorrectly. I say this based on personal observation. It's unfortunate because that should be a very easy problem.
 
My Dear Aunt Sally.

Here is where a lot of elementary and middle school teachers get it wrong. They use things like Please Excuse Me Dear Aunt Sally or PEMDAS which gives the impression that operations are done in the following order:
  1. Parentheses
  2. Exponents
  3. Multiplication
  4. Division
  5. Addition
  6. Subtraction
While actually it should be :
  1. Work inside parentheses if any
  2. Do exponents from right to left
  3. Do multiplication and divisions from left to right
  4. Do addition and subtraction from left to right
 
I can vouch ... you got it right!

One reason I don't subscribe to the acronym PEDMAS is that many think you do division before multiplication and addition before subtraction while the correct thinking is you do division and multiplication at the same level working left to right, same for addition and subtraction.
In general, acronyms in mathematics aren’t a good idea as they’re limiting. Everyone has heard of FOIL, right, for multiplying binomials. Once you get a problem like, say,
(2x+5)(3x^2+4x+3), what do you do?
 
Apparently this problem has been going around on FB and Twitter lately because Herbie and I had a discussion about this the other week. What follows is an old riddle which I’d like to try on youse. LHS= Left Hand Side.

1. Suppose that a=b.
2. Add a to both sides: a+a=b+a
3. Simplify LHS: 2a=b+a
4. Subtract 2b from both sides: 2a-2b=(b+a)-2b
5. Factor LHS, simplify RHS: 2(a-b)=a-b
6. Divide out a-b from both sides:
2(a-b)/(a-b)=(a-b)/(a-b)
7. Simplify to get 2=1.

Okay, obviously there’s a mistake. Where’s the mistake?
 
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Apparently this problem has been going around on FB and Twitter lately because Herbie and I had a discussion about this the other week. What follows is an old riddle which I’d like to try on youse. LHS= Left Hand Side.

1. Suppose that a=b.
2. Add a to both sides: a+a=b+a
3. Simplify LHS: 2a=b+a
4. Subtract 2b from both sides: 2a-2b=(b+a)-2b
5. Factor LHS, simplify RHS: 2(a-b)=a-b
6. Divide out a-b from both sides:
2(a-b)/(a-b)=(a-b)/(a-b)
7. Simplify to get 2=1.

Okay, obviously there’s a mistake. Where’s the mistake?
A-B is definitionally zero since you stated that A=B. Can't divide by zero.

But isn't the real problem that people are trying to foster the idea that math is subjective?

You should be speaking out against such nonsense.
 
It will take care of itself. Mathematics, like science, always wins in the end.
Yes, after starving millions of people to death, Lysenkoism was eventually discredited.

Hitler's theories on the Jewish people were also eventually discredited.

Sure wish good people would have stood up in 1937, though.

Weak, LionJim, Weak.
 
Yes, after starving millions of people to death, Lysenkoism was eventually discredited.

Hitler's theories on the Jewish people were also eventually discredited.

Sure wish good people would have stood up in 1937, though.

Weak, LionJim, Weak.
But what if we changed the rules? Wouldn't that make maths subjective? It's been done 19 times in this thread alone.
 
Yes, after starving millions of people to death, Lysenkoism was eventually discredited.

Hitler's theories on the Jewish people were also eventually discredited.

Sure wish good people would have stood up in 1937, though.

Weak, LionJim, Weak.
You’re bringing the Holocaust into the discussion?

What would you have me do? I’m retired. If I were still a college professor I suppose I’d ask my colleagues what we could or should do. But now this is my only forum. There are plenty of active mathematicians responding to this issue. Their voices will be heard and their voices will prevail, of that I have no doubt.

“Sure wish that good people would have stood up in 1937, though.” You don’t seriously think that people didn’t speak up in 1937, do you? Einstein did, Von Laue, Hilbert, Bohr. (Go wiki von Laue, he is a personal hero of mine.)

In the 1910s and the 1920s there was a push to promote “Ayran” mathematics and physics in Germany. This was pushed by some fairly prominent physicists and mathematicians, among them Stark, Bieberbach, and, later, Teichmuller. It failed because it was faulty physics, faulty mathematics. Mathematics always wins in the end.

These sorts of issues in mathematical pedagogy crop up pretty much constantly and always get shot down. To the layman, this sort of thing might seem alarming but to someone like Herb and myself, we see this all the time, someone comes with a new idea that just doesn’t work. A few years back people brought up the idea that somehow you could learn calculus without being fluent in algebra. Nobody talks about this anymore because it’s been totally discredited. I see this all the time, and believe me when I say it will take care of itself.
 
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You’re bringing the Holocaust into the discussion?

What would you have me do? I’m retired. If I were still a college professor I suppose I’d ask my colleagues what we could or should do. But now this is my only forum. There are plenty of active mathematicians responding to this issue. Their voices will be heard and their voices will prevail, of that I have no doubt.

“Sure wish that good people would have stood up in 1937, though.” You don’t seriously think that people didn’t speak up in 1937, do you? Einstein did, Von Laue, Hilbert, Bohr. (Go wiki von Laue, he is a personal hero of mine.)

Perhaps Lysenkoism is a better example of "bad science" and perhaps I should have stuck with that. Granted. It makes the logic easier to follow, as for many the Holocaust is a uniquely emotional event.

And yes, people did speak up. Obviously not enough.

But people on your side of the aisle (democrat) think you're the "go to" math guy on this forum. They will listen. I think you know that your voice would have more impact than my voice on this issue.

Here is the heart of the matter. Those who are saying that math is subjective are lying. They are not "mistaken", they're lying. You know they're lying and I know they're lying. I can't justify the lying.

In each case, you've argued that you should not correct people today because eventually the truth will become obvious. That's terrible, honestly. You are willing to let our educational system be destroyed because you don't want to correct idiots who happen to be your political allies.

I agree with you only in that your statement is probably true - eventually math and physics will win. But the cost (and we've already seen the cost as our technical competency erodes) is too high to wait.

How many posters on this board might go down a more honest, more truthful view of the world if you were to use your influence to say, "Hey guys, math and physics are NOT subjective. They're subject to empirical verification and falsification."
 
China is laughing their asses off.

Anyone who believes that math is subjective should never vote again.

Idiots. Morons.
Funny you say this... I presented the problem to my dad who got the correct answer.

He then googled it and said:
"The thing that I saw disturbing was the written discussion gave credence to 9 since that is what a calculator gave."

I responded:
"China is eating our lunch"
 
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