need help with determining a formula

[Cal]

open a spreadsheet and place the following value(s)...

(cell A1) $50000 ..., this entry represents a fixed dollar amount
(cell B1) 0.025 ..., this entry represents a "rate"
(cell C1) 25 ..., this entry represents a fixed amount of years
(cell D1) 0.020 ..., this entry represents a seperate "rate"
(cell E1) 5 ..., this entry represents additional amount of years
(cell F1's formula) =(A1*B1*C1)+(A1*D1*E1) ..., this produces $36250
(cell G1's formula) =F1/A1 ..., this produces 72.5%, (or .0725)
(cell H1's formula) is where I need help?

I cannot deterime the formula that will report, "What amount of total years
will produce a result of 78% (.078) in G1's cell? 25 plus "whatever"
additional years?
P.S. (C1+E1)/G1*.78 does not produce the correct formula/answer. I know
that the correct answer is, 32.75 (years) or otherwords 7.75 in E1's cell,
but I cannot figure out the formula that will provide that answer!

Thanks for your help...


-
rudy

 

[Bryan Hessey]

If I were good at maths I could answer this, but alas, I'm not
however:

your 72.5% in G1 is composed of 43103.54 being (A1*B1*C1) (and A1) a
72.5% and 6896.55 being +(A1*D1*E1) (and A1) at 72.5%

The 36250 is 31250 + 5000 of which 31250 will not change by adjustin
column E, so to calculate column E is then (A1 * .78 ) = 39000 (colum
F) of which you have 31250, thus you need 7750

If +(A1*D1*E1) needs to be 7750 then E1 = 7750 / (A1 * D1) or somethin
like that.

Hope this helps

 

[bpeltzer]

You could do this with goal seek. But if you want the equation, =(0.78 -
B1*C1)/D1