Split - Simplify - Need to follow PEMDAS

[schoolhelpnow.com]

reference: https://www.freemathhelp.com/forum/threads/simplify.127935/

Here is the explanation "not" in math terms:

18 and 45's largest common factor is 9 - divide both by 9 and you get 2/5

When it comes to the variables, stick the final answer where the largest exponent is.

Since this is division, subtract the exponents (don't worry about "where" it is, just do the bigger minus the smaller)

Here's what I mean:

Since the original problem was 18x^7y^8/45x^10y you can see that the larger x is on the bottom (10 vs 7) and the y is larger on the top (8 vs 1) so the final answer will have the x on the bottom and the y on the top:

2y^7/5x^3

Let me know if this makes sense!

 

[lookagain]

Since the original problem was 18x^7y^8/45x^10y

No, the original problem is the equivalent of 18x^7y^8/(45x^10y).
The denominator needs grouping symbols around it when you write it in
horizontal style.

so the final answer will have the x on the bottom and the y on the top:

2y^7/5x^3

This answer needs grouping symbols around the denominator as well:

2y^7/(5x^3)

 

[schoolhelpnow.com]

No, the original problem is the equivalent of 18x^7y^8/(45x^10y).
The denominator needs grouping symbols around it when you write it in
horizontal style.





This answer needs grouping symbols around the denominator as well:

2y^7/(5x^3)

Excuse me? First of all, I’m a math teacher. You don’t need to correct how I did the problem. We both ended up with the same answer. Secondly, I wrote that I was explaining it “not using math terms” to be as clear and direct as possible.

 

[Deleted member 4993]

Excuse me? First of all, I’m a math teacher. You don’t need to correct how I did the problem. We both ended up with the same answer. Secondly, I wrote that I was explaining it “not using math terms” to be as clear and direct as possible.

You wrote your answer as:

2y^7/5x^3 which is

= 2y^7/5 * x^3

That is INCORRECT answer to the original problem.

Incorrect answers can be clear and direct - but those are still INCORRECT.

You said - You don’t need to correct how I did the problem.

We all need to correct each other (as necessary) - so that the STUDENTS learn correctly.

Another point

Please change your user name - from a commercial URL to something more mundane.

If you do not change your USERNAME - your posts will not be approved - and you will be banned.

 

[schoolhelpnow.com]

You wrote your answer as:

2y^7/5x^3 which is

= 2y^7/5 * x^3

That is INCORRECT answer to the original problem.

Incorrect answers can be clear and direct - but those are still INCORRECT.

Perhaps it’s how it’s written (not using a real fraction set up) - but my answer is not incorrect. This is why kids hate math - because of people like you. If the OP turned in my answer, it would be correct.

Roger on the “more mundane name” coming right up!

 

[Deleted member 4993]

Perhaps it’s how it’s written (not using a real fraction set up) - but my answer is not incorrect. This is why kids hate math - because of people like you. If the OP turned in my answer, it would be correct.

Roger on the “more mundane name” coming right up!

Perhaps it’s how it’s written....

There is no perhaps about it - my (and LookAgain's) suggested way is the CORRECT way to learn it. It follows mathematical rule (PEMDAS or BODMAS)

Try to evaluate what you wrote in a calculator - put x=0 - and then think what should have happened.

I have taught engineering in University/College level. Multitude of your students flunked out because they did not follow PEMDAS (some probably your student).

If the OP turned in my answer, it would be correct - graded by you but not other 99.999% math-teachers (those who know the PEMDAS).

 

[topsquark]

This is why kids hate math - because of people like you. If the OP turned in my answer, it would be correct.

What the students need is for something to tell them how to read an expression the same way. If you are going to write things out in text that means you need to use parenthesis. Are you actually saying that if one calls it 2y^7/5x^3 and another calls it 2y^7/(5x^3) that it means the same thing?
[math]2y^7/5x^3 = \dfrac{2y^7}{5} \cdot x^3[/math]
[math]2y^7/(5x^3) = \dfrac{2y^7}{5x^3}[/math]
How can they communicate? This is the kind of problems that students have. I am especially qualified to comment on this because my Physics professors would make this kind of mistake all the time.

-Dan

 

[Steven G]

It is teachers like you that make students hate math by mis-teaching them. Why do you still use PEMDAS? Haven't you realized by now that it does not work? Or is it because you do not know other methods?

2nd warning. If you do not change your username very soon, I will ask that you be banned from this forum as it violates our policy.

 

[Deleted member 4993]

It is teachers like you that make students hate math by mis-teaching them. Why do you still use PEMDAS? Haven't you realized by now that it does not work? Or is it because you do not know other methods?

2nd warning. If you do not change your username very soon, I will ask that you be banned from this forum as it violates our policy.

Jomo,

Why do you say:

"Why do you still use PEMDAS? Haven't you realized by now that it does not work?"

I have not come across a problem in algebra where "it does not work". Have you?

By the way, s/he must have changed user name. That user last visited our forum on Feb 9. I edited out your statement.

 

[Steven G]

Jomo,

Why do you say:

"Why do you still use PEMDAS? Haven't you realized by now that it does not work?"

I have not come across a problem in algebra where "it does not work". Have you?

By the way, s/he must have changed user name. That user last visited our forum on Feb 9. I edited out your statement.

When I said that PEMDAS does not work I meant that teaching it does not work. Students have been taught this for ages and still mess up with it. Even if they do not make errors with it, it is something that they memorized but may not understand. I like to think that before you add/subtract that you need to know what you are adding/subtracting. The + and - signs, not inside parenthesis, divide the expression into its terms. Now before adding you need to know the values of the terms. All of my students who used this method (which I taught them) did quite well with this method. Other students of mine could not be bothered with thinking or learning a new method and insisted on using PEMDAS with mixed results.

 

[lookagain]

When I said that PEMDAS does not work I meant that teaching it does not work.

It sounds as if you are stating that this acronym does not adequately explain to students how to handle
the particulars and nuances that they do encounter at times when handling relatively more complicated
order of operations problems.

Maybe you could post one or two examples to illustrate the tendency of some students to make errors
while simplifying expressions after being taught PEMDAS as the method.

 

[Steven G]

It sounds as if you are stating that this acronym does not explain to students how to handle the particulars
and nuances that they do encounter at times when handling relatively more complicated order of operations
problems.

In theory it does but in reality students mess this up all the time. You know that! Identifying the terms and factors is much a clearer method.

 

[Deleted member 4993]

In theory it does but in reality students mess this up all the time. You know that! Identifying the terms and factors is much a clearer method.

Can you post a problem where students messed up using PEMDAS - yet your" alternatve" method is easier to implement!

 

[Steven G]

Can you post a problem where students messed up using PEMDAS - yet your" alternatve" method is easier to implement!

2+3*4 =5*4 =20

2 + 3*4 = 2 + 12 = 14

 

[Deleted member 4993]

2+3*4 =5*4 =20......................................Did not follow PEMDAS

Are you saying that PEMDAS became too complicated here??

 

[topsquark]

2+3*4 =5*4 =20

I don't think this is a problem with PEDMAS. I've seen a number of people write expressions this way but the fault is on their side because they aren't following the system. As the world in general uses PEDMAS or some other equivalent I don't see a problem.

-Dan

 

[Steven G]

2+3*4 =5*4 =20......................................Did not follow PEMDAS

Are you saying that PEMDAS became too complicated here??

PEMDAS is never complicated but students make mistakes all the time. If they bother to find the terms which are separated by + and minus signs, compute the terms and then add/subtract they will not make any mistakes (other then adding/subtracting incorrectly).

Please view this video here

 

[Steven G]

I don't think this is a problem with PEDMAS. I've seen a number of people write expressions this way but the fault is on their side because they aren't following the system. As the world in general uses PEDMAS or some other equivalent I don't see a problem.

-Dan

What you are saying is exactly correct, PEMDAS works fine all the time. Some students however do not use it correctly. That is the problem. Just because it works does not mean it is a good method to teach, that is my point. The fact that the world uses PEMDAS does not mean anything to me at all.

 

[Deleted member 4993]

What you are saying is exactly correct. PEMDAS works fine all the time. Some students however do not use it correctly. That is the problem. Just because it works does not mean it is a good method to teach, that is my point. The fact that the world uses PEMDAS does not mean anything to me at all.

So the word is meaningless (acronyms are that way) - so is SOHCAHTOA. But after using those ~500 times, those start to become useful.

 

[Steven G]

SO

So the word is meaningless (acronyms are that way) - so is SOHCAHTOA. But after using those ~500 times, those start to become useful.

SOHCAHTOA gives the definition of some trig functions very nicely. It is not a procedure as with PEMDAS!

SOHCAHTOA ==> S=O/H C=A/H and T=O/A