Could someone please check my results for this formula and maybe write
it out as to how it should be.. Just to make sure it's correct.
A3 is Total Liters Water 1431
B3 is Actual percent Solvent 12.1%
C3 is Recommended percent Solvent 17.5%
D3 is Increase percent 5.4%
F3 is liters added 94
What I'm doing is A3*(D3/0.825) but I don't think it should be
written this way.
Yes, that derives 94, the value that you specify for F3. But I don't
think 94 is the correct answer.
If you have 1431 liters of water and 12.1% of the total that you have
is solvent, you have a total of 1431/(1-0.12.%) liters -- about 1628
liters -- and you have about 1628-1431 liters of solvent -- about 197
liters.
As a double check, note that 197/1628 is about 12.1%.
If you want 1431 liters of water to be 1-17.5% of the total, the total
should be 1431/(1-17.5%) -- about 1734.55 liters -- and the amount of
solvent should be 1734.55-1431 liters -- about 303.55 liters.
As a double check, note that 303.55/1734.55 is about 17.5%.
So you need to add 303.55-197 liters of solvent -- about 106.55
liters, not 94.
Personally, I think B3 should be the amount of solvent that you
currently have, not the derived percentage. Then you might have less
computational error due to rounding. But perhaps you have no control
over that. (Homework?)
So, with the data you provide, F3 should be:
=(A3/(1-C3) - A3) - (A3/(1-B3) - A3)
which can be simplified algebraically to:
=A3/(1-C3) - A3/(1-B3)
Note: This assumes that you currently have separate water and
solvent; ergo, a negative amount in F3 makes some sense.
On the other hand, if water and solvent are already mixed in solution,
I think you need another cell (G3) to compute the amount of additional
water in the case when there is already too much solvent. And the
formulas for both F3 and G3 should not result in negative values when
the amount of their respective component already exceeds the
recommended percentage.
In that case, the formulas in F3 and G3 are more complicated. Do you
need help with those?
