how would I transpose r= PL/a

To make L the subject of the formula

Chur

I'm going to try and explain this in the way that I was explained it when I finally made sense of how to do this. Hopefully you will never need help transposing ever again!

The main rule of transposition:
If we take any equation and perform equal operations to both sides, then the equation remains the same

So, for example, we take the simple equation:

1 + 2 = 3

Now, this is obviously right. Now we apply the main rule of transposition, and add 2 to both sides (can be any number or operation, as long as we apply it to both sides):

1 + 2 + 2 = 3 + 2

You can see that the equation is still true, and that both equations are equivalent.

Now let's do it with variables. Let's say that

x + y = z

Now we can add 2 to both sides, and it's still true, namely

x + y + 2 = z + 2

If the first equation is true for a given set of x, y and z, then so is the second equation, because they are equivalent.

Now onto your question.

If we take x+y = z and now we subtract y from both sides, we find that

x + y - y = z - y or x = z - y

What we have now done is moved the y from one side to the other, we have made x the subject of the formula.


Now, if i take your formula

r = \frac{P*L}{a},

By the main rule of transposition, I should be able to divide both sides by P

This gives us:

\frac{r}{P} = \frac{P*L}{a*P} = \frac{L}{a}

As you can see, we have moved the P from one side to the other!

See if you can apply this rule to move the a to the other side in order to complete your question, and I'll give you help if you're having trouble with it!

But shouldn't it be something like L = blah blah. Without the a being under it, becoz I need that to figure out a question. Where I don't know L

I haven't completely done the question for you, read what I wrote, don't just look for the answer.

yeah but I can't work out this transposing stuff. So r/p = L/a, but I still don't know what to do next, do u divide them by a?

r(a)=PL--> (r(a))/p=L
you want to multiply out the denomenator on both sides, so kind of whatever you do on one side you have to do to both sides to keep them equal.
kind of like when you have x=2+y and you want y... you just subtract 2 from the one side to get x-2=y

hope this helps a little.. it's kind of hard to explain without pen and paper.

so it ends up being r x a / p = L

Yes

OK well I've got to work out this question, a copper conductor has a cross sectional area of 1.5mm squared and a resistance of 0.86 ohm, if the resistivity of copper is 17.24 nano ohm. What is the lengh of the conductor, I know that u go 17.24 x 10 power of -9 to convert that to ohm meters, and 1.5 x 10 power of -6 to get that to ohm meters, but it comes up with some weird answer when I work this all out, I'm guessing u do the same with resistance to convert that to ohm meters. By going 0.86 x 10 power of -6. any clues where I'm going wrong?

How to transpose formula L=4a - 8r + 2pie r subject is a?

Anyone caught spelling {\pi} as 'pie' will be sent to a work camp. :rolleyes:

Anyone caught spelling {\pi} as 'pie' will be sent to a work camp. :rolleyes:

some people don't know how to type the symbol for pie. Namely myself:)

I was just teasing because it is spelled 'pi', not 'pie'. It's a Greek letter, not a pastry.

But, if you want to use LaTex type {\pi} surrounded by the tags.

Except put a slash in the last tag like so [/math]

I tried to fix this last post but it will not let me for some reason.

Peter Karl, did you read what Capuchin said in his first post? If not, do so because I'm pretty sure that you'll understand how to solve your problem.

I can write pi! \pi

lol okay I get it... I didn't even realize the spelling. I just type and go, if you know what I mean (and I thought you meant the symbols)

while we're on the topic though... how do you put the pi symbol in instead of writing it?

LaTex.

For instance:

\int_{a}^{b}f(x)dx

Some Greek letters:

{\alpha}, \;\ {\beta}, \;\ {\gamma}, \;\ {\delta}, \;\ {\epsilon}

Click on 'quote user' at the bottom of my post to see the code I typed to make it display that way.