rearranging formulas

[cocaine]

ahh i cant stand these haha they make me want to tear my hair out.

im very good with other aspects of maths, just so you know im not a complete idiot haha. but rearranging formulas to make one letter the subject of the formula is my downfall.

heres an example:
Make q the subject of the formula

P = 2q + 10

can anyone write down steps for what you need to do for that? thanksss

edit: hang on, is this right

p-10=2q

so q = p-10 OVER 2

?

[Jesus-Egg]

Yes, that is correct.

Rearranging formulae is usually fairly simple. Just keep practicing until you get the hang of it, and you'll be fine. You just need to remember to follow the following steps:

If, for example, you want to make a the subject:

- Multiply through to get rid of any fractions

- Collect all of the terms with a in on one side of the equation, and move all the terms without an a to the other side

- Factorise, so you have a multiplied by something, which i'll call B

- Divide through by B, and you're done

Example:

c = (2a -3b)/5a

and you want to make a the subject

- Multiply by 5a to get rid of the fraction

5ac = 2a -3b

- Collect all the as to one side of the equation

2a - 5ac = 3b

- Factorise

a(2 - 5c) = 3b

- Divide

a = 3b/(2 - 5c)

[Barmi]

Get used to rearranging equations... you need to do it for a lot of maths past GCSE (if you plan on pursuing it).

The best thing to do is practice. Do plenty of difficult questions until you are sick to death of them. You will feel like you are invincible. Then you face Integration and realise all is lost.

[Supersam]

Get used to rearranging equations... you need to do it for a lot of maths past GCSE (if you plan on pursuing it).

The best thing to do is practice. Do plenty of difficult questions until you are sick to death of them. You will feel like you are invincible. Then you face Integration and realise all is lost.

And then you realise that maths beyond GCSE is just crazy and Integration is only the start of your worries.

[Barmi]

And then you realise that maths beyond GCSE is just crazy and Integration is only the start of your worries.
I found everything easy at A-level bar Integration. :(

[AJKHoosier1]

if you can't rearrange formula's, you are screwed when it comes to relativity
and the one itt is like omg ezz

[le harry]

I found everything easy at A-level bar Integration. :(
you noob integration is easy. matrices :@

[luce]

Get used to rearranging equations... you need to do it for a lot of maths past GCSE (if you plan on pursuing it).

The best thing to do is practice. Do plenty of difficult questions until you are sick to death of them. You will feel like you are invincible. Then you face Integration and realise all is lost.

you don't need to that much to pass GCSE! Also A level isn't much harder then GCSE. Not what i've done of it anyway, i haven't started C4 yet though :rolleyes:

[Soka]

Hardest topic i've seen in this thread in my opinion is matrices by harry. Comes up in FP1 in the UK.. matrices row operations are awful.

Barmi, i've sent you another PM regarding uni's!

Cocaine, just remember that whatever you do to one side you must do to the other.

Also order is important when rearranging:

Addition and Subtraction first
then
Division and Multiplication.

The key really is to practice, practice and practice then it will all just be done naturally :)

So using yours as an example

P = 2q + 10
P - 10 = 2q + 10 - 10 (subtraction first.)
(2q)/2 = (p - 10)/2 (division last)
Hence;
q = (p - 10)/2

i've included the strike through parts to show that the operation has being carried out on both sides. I'm sure you don't need the strikethrough parts!

[--ss--]

You basically move figures to the other side by doing the inverse operation to it, so lets say on the right hand side you have a +10, as you want to make the letter on the left hand side the subject you gotta move the +10 to the other side so you'll make it -10. actually i'm not too sure what i'm talking about, it's quite easy when you get the hang of it, have you tried using mathswatch on the net somewhere?

[clueless]

once its clicked you will be able to do them real easy

just always remember to do the same to each side

if you -10 on one side you -10 on the other

and its BODMAS backwards
and always do it step by step to save confusion!

[Jesus-Egg]

matrices row operations are awful.

huh? We've just been doing about matrices at uni, and the row operations are all fairly easy. What is it you find difficult?

[Soka]

huh? We've just been doing about matrices at uni, and the row operations are all fairly easy. What is it you find difficult?

I'm ok with inverse matrices, the addition/subtractions etc, and using the matrices algebra to solve equations (such as the common way to find solutions is AX^-1 = V). But I find it pointless, (I probably used the wrong word, difficult earlier) to solve equations using the row operations thing similiar to the simplex algorithm in D1.. its annoying in that when you do one row wrong with a simple slip on arithmacy the whole thing can go wrong and you have to start again. Also theres a much more efficient way to solve it by using the matrices algebra. We are talking about the same row operations here aren't we? Anyways what you using matrices for, as aren't you doing physics? :P

[Jesus-Egg]

Yeah, I know what you mean, it is really easy to make mistakes. I think we are talking about the same operations: swapping rows, multiplying rows by a constant, and replacing a row with itself plus a multiple of a different row. We've mainly been doing matrices to solve linear systems with lots of unknowns, but we've just done about determinants, and how you can use the determinant as an easy way to remember how to do the vector product. Yeah, i'm doing physics, but we have to do 2 maths modules this year, because there is quite a lot of maths involved in the physics. There's loads of calculus, vectors, etc

Oh, and I hated the simplex algorithm! I did AS further maths, and had to teach myself D1. There was this, and something else that I didn't really understand that well (can't remember what the other one was), and of course they both came up in the exam...

[Soka]

Yeah, I know what you mean, it is really easy to make mistakes. I think we are talking about the same operations: swapping rows, multiplying rows by a constant, and replacing a row with itself plus a multiple of a different row. We've mainly been doing matrices to solve linear systems with lots of unknowns, but we've just done about determinants, and how you can use the determinant as an easy way to remember how to do the vector product. Yeah, i'm doing physics, but we have to do 2 maths modules this year, because there is quite a lot of maths involved in the physics. There's loads of calculus, vectors, etc

Oh, and I hated the simplex algorithm! I did AS further maths, and had to teach myself D1. There was this, and something else that I didn't really understand that well (can't remember what the other one was), and of course they both came up in the exam...

Yeah, my brothers doing a Masters in Physics with Maths and he says he prefers the maths modules :P I think the maths modules will help the physics a great deal, I'm guessing there will be a lot of advanced calculus in physics. I can't think of anyone who does like the simplex algorithm lol. It comes up in the exam every year though because theres so little topics in D1 so everything practically comes up on the paper. D1 has now being shifted to D2 in the new specs. to make D1 easier apparently :rolleyes:. Of course, I would be doing D2 in June this year so I have to do Simplex again.

[Jesus-Egg]

haha, have fun! They're making D1 easier? It was already easy to begin with (apart from a couple of bits)! Anyway, yeah, the maths modules are better than the physics ones. We had collection exams when we got back after christmas, and in each exam you need 40% to pass. In the maths modules, most people did fairly well, but we got an email saying that in the physics exam 100 (out of 230) people failed! I'll find out what I got tomorrow in my tutorial, but i'm fairly confident i've passed. And yeah, there's lots of calculus, especially in classical mechanics. I hate moments of inertia! :( I mean, the formula's simple enough,
http://upload.wikimedia.org/math/4/0/3/403ab94a798c5c1c64af3e569e17b603.png
but you have to change variables, and if it's a strange shape it gets very confusing!

[clueless]

oh jeez your maths talk is alien to me and im meant to be doing it for a level next year!
sigh fun things to come eh?

[Jesus-Egg]

oh jeez your maths talk is alien to me and im meant to be doing it for a level next year!

Don't worry about it, A level math's isn't too bad. There are quite a lot of new things that you'll probably never have done before, such as differentiation, integration, logarithms, trig identies etc, which might be a bit confusing to start off with, but once you get the hang of them, they're ok.


sigh fun things to come eh?

Maths is always fun! unless it's the simplex algorithm

[cocaine]

guys, calm it, all i needed was a bit of GCSE maths help :(!!