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New Member
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Apr 5, 2008, 03:06 PM
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Transposing formulas
how would I transpose r= PL/a
To make L the subject of the formula
Chur
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Uber Member
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Apr 5, 2008, 03:42 PM
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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:
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):
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
Now we can add 2 to both sides, and it's still true, namely
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 and now we subtract y from both sides, we find that
or
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
,
By the main rule of transposition, I should be able to divide both sides by P
This gives us:
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!
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New Member
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Apr 5, 2008, 05:30 PM
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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
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Uber Member
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Apr 5, 2008, 06:10 PM
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I haven't completely done the question for you, read what I wrote, don't just look for the answer.
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New Member
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Apr 5, 2008, 07:52 PM
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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?
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Expert
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Apr 5, 2008, 08:06 PM
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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.
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New Member
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Apr 6, 2008, 12:34 PM
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so it ends up being r x a / p = L
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Expert
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Apr 6, 2008, 06:21 PM
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Yes
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New Member
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Apr 6, 2008, 11:38 PM
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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?
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New Member
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Sep 28, 2008, 01:32 AM
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How to transpose formula L=4a - 8r + 2pie r subject is a?
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Ultra Member
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Sep 28, 2008, 06:03 AM
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Anyone caught spelling as 'pie' will be sent to a work camp. :rolleyes:
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Expert
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Sep 28, 2008, 06:06 AM
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Originally Posted by galactus
Anyone caught spelling as 'pie' will be sent to a work camp. :rolleyes:
some people don't know how to type the symbol for pie. Namely myself:)
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Ultra Member
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Sep 28, 2008, 06:24 AM
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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]
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Ultra Member
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Sep 28, 2008, 06:26 AM
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I tried to fix this last post but it will not let me for some reason.
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Uber Member
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Sep 28, 2008, 07:19 AM
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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!
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Expert
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Sep 28, 2008, 12:04 PM
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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?
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Ultra Member
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Sep 28, 2008, 12:07 PM
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LaTex.
For instance:
Some Greek letters:
Click on 'quote user' at the bottom of my post to see the code I typed to make it display that way.
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