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June 2nd, 2014, 02:37 AM   #1
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simple transposition

Hi

I cannot work out how to transpose formula examples that have a division on one side.

eg 15/x = 3



to get x on one side my first thought is to perform something regarding the 15 to give me 15/3 on the RHS. But I don't think I can really do this, and I have to follow a two step process such as divide multiply both sides by x

15 = 3*x then divide both sides by 3

I kind of see why I try to do some illogical(sadly it seems logical to me) initial calculation with the 15 to single out the x.

Is it always a two step process?

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June 2nd, 2014, 07:36 AM   #2
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$\displaystyle \frac{a}{b} = c \Rightarrow a=bc \; \& \; \frac{a}{c} = b$

$\displaystyle ab=c \Rightarrow \frac{c}{b} = a \; \& \; \frac{c}{a} = c$

It's basic arithmetic.
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June 2nd, 2014, 05:36 PM   #3
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Remember that 15/x = 3 is "really" 15/x = 3/1

And:
if a/b = c/d then a*d = b*c

So:
15*1 = 3*x
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June 3rd, 2014, 12:16 AM   #4
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Quote:
Originally Posted by rightsidedbrain View Post
Is it always a two step process?
Divide each side of the equation 15/x = 3 into 15.
That gives you 15/(15/x) = 15/3, i.e. x = 5.
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