# Solve for P

Solve for P:

$$\frac{p - 10}{-5}=\frac{p - 1}{4}$$

The most effective way i will learn this embarrassingly simple problem is if you post the solution and i will easily be able to examine it.

thank you in advance

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## Answers and Replies

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is the answer 6 1/3?

show your steps, don't be embarassed.

$$\frac{p - 10}{-5}=\frac{p - 1}{4}$$

$$p - 5 =\frac{p - 1}{4}$$

$$4p - 20 = p - 1$$

$$3p -19 = 0$$

$$3p = 19$$

$$p = 19 / 3$$

p = 6 1/3

cristo
Staff Emeritus
Science Advisor
Your first line isn't right: what happened to the -5 in the denominator of the left hand side? To start with, I would multiply both sides up by the respective denominators, so you are left with 4(p-10)=-5(p-1). Can you go from here?

HallsofIvy
Science Advisor
Homework Helper
Solve for P:

$$\frac{p - 10}{-5}=\frac{p - 1}{4}$$

The most effective way i will learn this embarrassingly simple problem is if you post the solution and i will easily be able to examine it.

thank you in advance
No, it is not. The most effective way to learn anything is by doing it. Many students fool themselves into looking at a solution by someone else and saying "yes, I understand that now"- but then not being able to repeat even the solution to that problem later much less a different problem of the same sort. What have you tried?

Personally, I hate fractions. What could I do to get rid of the denominators?

Your first line isn't right: what happened to the -5 in the denominator of the left hand side? To start with, I would multiply both sides up by the respective denominators, so you are left with 4(p-10)=-5(p-1). Can you go from here?
4(p-10) = -5(p-1)

4p-40 = -5p+5

4p+5p = 5+40

9p = 45

p = 45/9

= 5

is this correct?

Plug that value into your original problem and see if the left equals the right.

yes thank you

$$\frac{p - 10}{-5}=\frac{p - 1}{4}$$

$$p - 5 =\frac{p - 1}{4}$$
I just wanted to jump in and explain something here. The reason your left side operation is illegal is this: You can only do shortening on complete expressions. "+" and "-" divides expressions into parts. So, "A" is an expression, so is "4A" or "4 * 8 * 9". While "A + 1" is in fact two different expressions combined, and so is "4A - 2B" or "4 * 8 + 9".

You can shorten these:
$$\frac{a * b}{b} = a$$

$$\frac{10 * 5}{5} = 10$$

But not these:
$$\frac{a + b}{b}$$

$$\frac{10 + 5}{5}$$

If you want to shorten a combined expression, you need to shorten the entire thing. You can put parentheses around it and call the whole thing a single expression: (A + 1) is an expression, but to shorten it you need an (A + 1) expression in the denominator as well.

So, you CAN shorten this:
$$\frac{a + b}{3(a + b)} = \frac{1}{3}$$

Shortening works because a fraction is really a division, and a*b divided by b equals a. If you multiply by something, and then divide by the same, you get the original amount. So you simply remove multiples and divides of the same nomination.

There is a deeper understanding obtainable here, this whole thing is based on certain laws of multiples (like, the order doesn't matter: A * B = B * A) and divisions, which you can look into if so inclined. I assure you, if you start with those laws and build your way up to the fractions, everything will be much clearer. It takes more time, but it is easier than memorizing rules, in a way.

Caveat emptor: English is a second language to me, so some of the terms I use might not be appropriate. "Expression" might in fact be "Factors" or some such.

k

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thanks kenewbie, that gives me something to experiment with. Also, I find that playing around with these rules and just experimenting with concepts in general is making Algebra more and more natural to me ;)

No, it is not. The most effective way to learn anything is by doing it. Many students fool themselves into looking at a solution by someone else and saying "yes, I understand that now"- but then not being able to repeat even the solution to that problem later much less a different problem of the same sort. What have you tried?

Personally, I hate fractions. What could I do to get rid of the denominators?

u might of misunderstood what i meant.. what i meant was: "just post the solution (as i will understand it without additional commentary) and so i can get on with applying it to similar examples " :)

u might of misunderstood what i meant.. what i meant was: "just post the solution (as i will understand it without additional commentary) and so i can get on with applying it to similar examples " :)
You misunderstand what Halls is saying. I tutor a lot of people for Algebra, and they always ask me to work a problem. After working it, they are like omg wow that makes so a lot sense ... I ask them to WORK THE SAMEEE PROBLEM, they can't do it. So I would listen to what Halls is saying. Be aware of what you are doing, Math is too important to brush off.

So I would listen to what Halls is saying. Be aware of what you are doing, Math is too important to brush off.

Thread after thread after thread im getting the same thoughtless comments.

I do take math seriously. My degree is based on math. Im a 20 year old second year Applied Finance / App Statistics student at top 8 Australian uni, apart form this algebra am currently undertaking I am also currently taking calculus, statistical modelling (in matlab), acounting and economics. As mentioned, im SECOND year and i have ALREADY achieved above average outcomes in my first year.

I am just here to bridge some serious gaps in my algebra knowledge that i have forgotten since last completing a pure math course 3 years ago at high school. Is that sooo hard to believe. I have already PROVEN learning outcomes at university including several math (finance) units from my first year.

What’s the point of this boring rant u might be wondering? Well.. it seems u have ASSUMED that im some lazy 6th grade student in elementary school trying to get some one else to do my homework so I can go play some video games.

Its true and you know it.

So everytime i ask a question someone manages to throw in some pointless distractions instead of just posting MATH

You see, when ever I post a math (finance) questions here:

www.wilmott.com

or when I post my C++ questions here:

www.mql4.com

I ALWAYS get ANSWERS instead of tips on how to study effectively or some other retarded comment.

Thank you to kenewbie and cristo for actually posting some math.

besides the help by the people mentioned above, I feel like im in a special ed class here.

so maybe im on the wrong forum?.. and yes, its rhetorical.

please ban my account, i dont care .

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The philosophy here is that if you show work people, can help you by pointing out flaws. Posting answers by other members is discouraged because overall people tend not to learn this way. It's like reading a proof, you might understand it as you read it, but could you reproduce the desired result? Probably not the first time around. If you however could derive that proof, you'd not only know it, but know the underlying concepts that it represents.

That said no one is going to ban your account. I think you've got a misunderstanding. When someone asks to see your work it is merely to see where you are in the process of finding a solution. Without some work ('even 'I have no clue where to start' helps) the people who are actively posting advice here do not know where to begin.

EDIT: Also verbal math skills are important to have as well. Being able to understand hints constructed in sentences as opposed to equations is a good skill to have.

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If you however could derive that proof, you'd not only know it, but know the underlying concepts that it represents.
isnt that obvious? u should trust the student to do the responsible thing and look for the concepts in the solution first. Especially when the question is of such horrid simplicity.

instead all i got was more questions as if its an interactive-learning-special-ed-class.

and theres nothing inherently wrong with that, but its painful and degrading when im in the middle if a bachelor's degree.

well i guess its no-ones fault but my own. I have nothing against PF's teaching philosophy, like i said, im on the wrong forum.

So, you CAN shorten this:
$$\frac{a + b}{3(a + b)} = \frac{1}{2(a + b)}$$

k
wait it is just me being tired or that is wrong. Shouldn't it be 1/3 not 1/2(a+b). maybe i didn't real before it.

isnt that obvious? u should trust the student to do the responsible thing and look for the concepts in the solution first. Especially when the question is of such horrid simplicity.

instead all i got was more questions as if its an interactive-learning-special-ed-class.

and theres nothing inherently wrong with that, but its painful and degrading when im in the middle if a bachelor's degree.

well i guess its no-ones fault but my own. I have nothing against PF's teaching philosophy, like i said, im on the wrong forum.
Well no offense but it was a pretty basic question. :uhh:

Questions like these are usually asked by younger people, so I guess people just assumed that you were younger, and that's why it sounded like they were preaching to a "special ed" class, that would be my guess. But you make a good point I think a lot of people are guilty of that.

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Questions like these are usually asked by younger people, so I guess people just assumed that you were younger, and that's why it sounded like they were preaching to a "special ed" class

exactly. so as a hint, i said 'just write the solution' in post #1

and look at the remarks i got in return.

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wait it is just me being tired or that is wrong. Shouldn't it be 1/3 not 1/2(a+b). maybe i didn't real before it.
Aye, you are of course correct. Can I blame the flex? It is the popular way out :)

k

cristo
Staff Emeritus
Science Advisor
So everytime i ask a question someone manages to throw in some pointless distractions instead of just posting MATH

You see, when ever I post a math (finance) questions here:

www.wilmott.com

or when I post my C++ questions here:

www.mql4.com

I ALWAYS get ANSWERS instead of tips on how to study effectively or some other retarded comment.
Physicsforums has been around for quite a while now (I wasn't around when it started, but many members here were) and gradually the homework forums here have grown, as has the policy. It is against PF policy to give straight out solutions to homework questions. Also, you should note that everyone who helps out here with your homework is a volunteer, and further a lot of us have experience tutoring or even lecturing, thus we know that most students do not benefit from receiving full solutions, contrary to their own belief.

Now, I understand that you are feeling like we're treating you like a little kid, but you've got to realise that if we just gave the solutions out to people's homework then it would be doing no service and I, for one, would not participate here. The thing that makes tutoring, whether it be online or face to face, enjoyable is seeing students learn, not telling students how to get a good mark in a class.

Yes, okay, so your question wasn't all that difficult, and clearly you'd just messed up in one line (which is why I pointed out where you had gone wrong) but you cannot expect people to provide you with solutions, without having an attempt at the question after the error has been pointed out to you.

Anyway, that's all I've got to say. I hope you don't leave PF, since it's never good to see a member go!