can I express X*4 in a formula?

P

paperguy

I am trying to create a formula in a spreadsheet that will calculate the
numeric value of "X" in the following formula;
X*4+55-X*.2=55*.79

Is this possible?
 
J

JE McGimpsey

Well, you could start out by doing some basic algebra:

X: =(55 * 0.79 - 55)/(4 - 0.2) ===> 43.45

Generalizing:

X * A1 + B1 - X * C1 = D1 * E1

X: =(D1 * E1 - B1)/(A1 - C1)
 
P

paperguy

Thank you for your prompt reply!
I do not have a problem doing the algebra, I am trying to write a formula to
do this in my worksheet since I will be using this formula over and over.

I am using my worksheet to set up a mass balance for multiple mixtures. The
correct formula for this is actually the one I wrote below. Where I have a
known output of "55gals. at .79% solution" and input "A" where only the 4%
solution is known and input "B" where only .2% solution is known.

This is why input "A" is expressed as Xgals*.4 and input "B" is expressed as
55-Xgals*.2%

I have set up my worksheet so that cell A1 will receive the numeric value of
X.
Cell B1 is 4 (the known 4% solution value in input "A")

Cell E1 will receive the numeric value of 55-X.
Cell F1 is .2 (the known .2% solution value in input "A")

Cell I1 is 55 (the known Gallons of the output)
Cell J1 is .79 (the known .79% solution value in input "A")
 
J

JE McGimpsey

First, while I did the algebra, I didn't do the math - the 43.45 was the
result of each side of the equation. X obviously = -3.039473684...

Which is a weird result for a volume. I suppose what you really meant
was:

X * 4 + (55 - X) * 0.2 = 55 * 0.79

which then becomes


X = ((55 * 0.79) - (55 * 0.2)) / (4 - 0.2)

or

X = (55 * (0.79 - 0.2)) / (4 - 0.2)

or

X = 8.539473684

which is much more reasonable, being positive.

Using your cell references, then


A1: =(I1 * (J1 - F1)) / (B1 - F1)
E1: = I1 - A1
 
P

paperguy

Dear JE McGimpsey,
You are absolutely correct about the equation!

And I want to give you kudos for your assistance. Your input was very
valuable and greatly appreciated!

Sincerely,

Jon Hutto (Paperguy)
 
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