Find D in A: Transposition Help

[Tweaked9107]

Just need a bit of help with this.

A = ( ( 2 X pi X k X L ) / (Ln(1.041) ) X (D - E)

I know everything except D. How do i find it?

 

[mathman]

Just need a bit of help with this.

A = ( ( 2 X pi X k X L ) / (Ln(1.041) ) X (D - E)

I know everything except D. How do i find it?

The expression needs clarification.

Are all the variables scalars? (I presume so)

In that case: step 1 - move everything except (D-E) to the left side and get:

D-E = A Ln(1.041)/( 2 X pi X k X L ) (I switched left and right)
Now add E to both sides.

 

[tiny-tim]

Hi Tweaked9107!

Just need a bit of help with this.

A = ( ( 2 X pi X k X L ) / (Ln(1.041) ) X (D - E)

I know everything except D. How do i find it?

(please write a small x, or *, for "times" )

That's of the form A = B/C(D - E) …

multiply both sides by (D - E), then expand that bracket, then shove the E stuff over to the RHS

 

[Tweaked9107]

In it's actual form it's:

Heat Transfer = ((2 * pi * heat coefficient * length) / Ln(Outside Diameter - Inside Diameter)) X (Inside Temperature - Outside Temperature)

That gives you heat transfer. My problem is i know all the figures for one end of the pipe to give me an answer. But I'm now trying to calculate what the inside temperature is further along the pipe. Whether than takes away any vagueness I am not sure?

 

[HallsofIvy]

Is the D- E in the numerator or denominator of your original fraction? mathman is assuming it is in the numerator, tiny-tim is assuming it is in the denominator.

 

[Tweaked9107]

Is the D- E in the numerator or denominator of your original fraction? mathman is assuming it is in the numerator, tiny-tim is assuming it is in the denominator.

I'll be perfectly honest. I have no idea what you mean.

 

[berkeman]

I'll be perfectly honest. I have no idea what you mean.

Your equation is ambiguous in the last term. Is it multiplying the numerator or denominator?

Can you use more parenthesis to remove this ambiguity?

 

[tiny-tim]

he means, is it on the top or the bottom (of the fraction)?

(and parentheses are brackets )

 

[Ray Vickson]

I'll be perfectly honest. I have no idea what you mean.

He means: is it $$A = \frac{2 \pi k L}{\ln(1.041)} (D-E)= \frac{2 \pi k L (D-E)}{\ln(1.041)}$$ or is it
$$A = \frac{2 \pi k L}{\ln(1.041) (D-E)}?$$

If you mean the first form you should write it as 2 pi k L (D-E)/ln(1.041), but if you mean the second form you should write 2 pi k L/[ln(1.041) (D-E)]. Use brackets.

RGV

 

[Tweaked9107]

The first one was correct yes. So the first reply by mathman was correct. Thanks for your help guys, and sorry for posting in the wrong section.