I think I may have misunderstood slightly what you want to do. The algebra I
gave was starting with a tank with 0% sealant and adding sealant to end up
with 17.5% sealant by volume. I now see that you may in fact start with a
tank that already contains some sealant i.e. B3 is not necessarily 0.
If I've now understood better, you want to calculate the volume of sealant
to be added to go from whatever % you start with (given by B3) to the value
in C3 (17.5%).
If that is now correct, then the algebra changes. Your starting point is a
volume Vo (tank size that you say is fixed at 1432 litres). That is made up
of B3% of additive and (100-B3)% of water (or whatever the base fluid is).
i.e. the volume of base fluid is (Vo*(100-B3)/100).
You want to end up with a volume V1, that is made up of C3% of additive and
(100 -C3)% of the base fluid. So the volume of base fluid is
V1*(100-C3/100).
Since the amount of base fluid does not change, we can write
V1*(100-C3)/100 = Vo*(100-B3)/100, or
V1= Vo*(100-B3)/(100-C3)
But V1 also is equal to your initial volume, Vo, plus the amount of sealant
added (= F3)
So V1 = Vo + F3 = Vo*(100-B3)/(100-C3)
Therefore
F3 = Vo ((100-B3)/100-C3) -1) = Vo*(C3-B3)/(100-C3)
Since you say that D3 contains the % increase by volume of sealant, (i.e D3
= (C3 - B3)), we get
F3 = Vo*D3/(100-C3)
Hope I got what you want right this time
'Tank Sizes'!$F$6*D3/C3/4.714)
To get 302 liters I have to divide 82.5/17.5 which is 4.714 is that
correct? I'm confused about the 4.714. Thanks so much for your help!!!-
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Here is the way I have it formatted.
Actual formula: =IF(OR(B3="",C3="",B3>C3),"",'Tank Sizes'!$F$6*D3/
C3/4.714)
"Date"
"Actual % by Volume Concentration"
"Recommended % by Volume"
"Increase% by Volume "
"Decrease g/l"
"Liters added"
"Gal. added"
"Next ScheduledTest"
23-Sep-2010 0.0% 17.5% 17.5% 304 80.24 23-Oct-2010
