Anyone ridiculously good with algebra (excel math question)

[shdw01]

I have 5 columns (A-E)

A = given
B = given
C = manually input (percentage)
D = A* (1-C)
E = (D-B) / D


For Example:

A= 10
B= 2
C= manually input 55%
D= 4.50 (10 x 45%)
E= 56% (4.5-2=2.5 2.5/4.5 = 56%)


if I change E to 56% (instead of a formula), can I make a formula for C? (currently manually input)

 

[shdw01]

someone told me it isn't possible and i disagreed, but I'm too stupid to figure out the answer

 

[Mopisgood]

not possible.

 

[kcameron95]

If I understand correctly what you are saying, no its not possible. If you do that, then D/E are independent of each other. However to figure out what D, you still need C. So C/D are defendant each other, so you need to have value for C or D (meaning you have values/not variables in one of those two).

 

[artiesliver]

I don't believe it is possible b/c I believe you will get a "circular reference" error.

 

[wolfie_cr]

C = (a-b-E*d) / A

does that work?

 

[kcameron95]

C = (a-b-E*d) / A

does that work?

No because E is no longer a formula. Its 56%, thus has no relationship with D.

 

[wolfie_cr]

wait wait now I am getting confused , it must be the beers

E=56% but that doesn't invalidate the relationship between d & b, does it?

 

[shdw01]

really? I understand there is a circular reference.

I think maybe columns C and D have to have new formulas but with A, B, and E as constants,

 

[wolfie_cr]

the new problem would be

A,B & E known

E=(D-B)/D (Which remains valid) , B&E known you get D

D=a(1-c) , a known and we got D from the first relationship we now get C

 

[seriousaddiction]

Im confused looking at this...I only got to Calculus 3 in college


I'll never forget my first and last day of that class

Welcome to grown up math. If I can tell you do not like math and are taking this course as a requirement I will fail you. I like math and being in my class I expect you to like math also.....seriousaddiction grabs laptop and cellphone and walks out the door changing his major and beginning the butterfly effect that changed my entire life


best decision i ever made...this thread gives me eeeeery memories

 

[wolfie_cr]

different way to express it would be

with A,B and E known we calculate D by doing

D= B/(1-E)

with D now known we calculate C by doing

C=1 - (D/A)

 

[wolfie_cr]

I think maybe columns C and D have to have new formulas but with A, B, and E as constants,

hopefully you are sober unlike yours truly, try the formulas below and see if it works

D= B/(1-E)

C=1 - (D/A)

 

[shdw01]

holy shit, i think you did it....

wolfie, you are now officially the smartest person on the rx....

according to me (a retard)

 

[wolfie_cr]

I am glad it worked!, in college I made it way past calculus 3.....and was pretty good at it.......fast forward 10 years....and now even a system of two equations puts my brain to work.......and my pride to sweat! :smoking:

 

[Waz]

This would have been much easier using Goal Seek in Excel.

 

[niltes]

this is actually pretty simple. wolfie is correct.
i would say this is an algebra 2 problem.

here are the steps

given this formula

d=a*(1-c) solve for c

first divide both sides of the equation by (1-c) giving

d =a*(1-c)
---- ----
(1-c) (1-c)

the (1-c) on the right side cancel each other out leaving

d = a
----
1-c

our goal here is to isolate c. these next 2 steps can be done in either order. divide both sides by d giving

d = a
--- ---
d(1-c) d

the d on the left side cancels leaving

1 = a
---- ----
1-c d

now flip the both sides of the equation bringing c to the top

1-c = d
--- --
1 a

or simplifying more

1-c = d/a

subtract 1 from both sides of the equation leaving

-c = (d/a) -1

multiply both sides by -1 to get the c rather than -c leaving

c= -(d/a) +1

or better still

c = 1 - (d/a)

VOILA. good job wolfie. end of lesson

 

[niltes]

the math is correct, but i am having trouble with the graphics keeping
the formulas looking correct. sorry

 

[NES]

This thread needs some titties.

 

[HuskerFan1]

damn some of you mofo's are SMART...

i feel like an idiot after reading this thread and i consider myself a fairly smart person...

probably should go drink some beers help make myself feel better:drink: