Sove this equation

[Richard Ruda]

I'm trying to get x on one side of this equation (solve for x )so I can
enter it into excel but my math skills are poor.

(43.75+x%) -7.5% = 50.31

43.75, 7.5% or 7.5/100 and 50.31 exist in cells I've created so I need to
put the formula in a cell to solve for x.
Any help from you mathematicians would be appreciated.

Thanks

Richard

 

[Bob Umlas]

algebraically:
43.75+x%=50.31+7.5%
x%=50.31+7.5%-43.75
x=(50.31+7.5%-43.75)*100

So, if A1 is 43.75, B1 is 50.31, C1 is 7.5%:
x=(B1+C1-A1)*100

 

[Richard Ruda]

Hi Bob,
Thanks for your reply but it's not correct.
Just test it by going back to the original formular. That is why I am having
probelms. If you take the result of your equation (solve for x) and add it
back to the original formula it will not come out to 50.31
By deduction, the result of x is somewhere around 24.5
That is:
43.75 + 24.5% = 54.47
Then 54.47 - 7.5% = 50.38 (close to 50.31)

Stumped but I'm sure it's simple but I'm rusty on this
Richard

 

[Peo Sjoblom]

You are wrong, Bob's result is correct


(43.75+x%) -7.5% = 50.31

gives

(43.75+663.5%)-7.5%=50.31

or

(43.75+6.635)-0.075=50.31

or

=(43.75+6.635)-0.075


equals 50.31

--
Regards,

Peo Sjoblom

(No private emails please, for everyone's
benefit keep the discussion in the newsgroup/forum)

 

[hgrove]

Richard Ruda wrote...

Thanks for your reply but it's not correct.

He was correct as he interpretted your formula, which is how Exce
would have interpretted the formula.

43.75 + x%

If x were, say, 10%, the expression above can be interpretted as 43.7
+ 0.10 = 43.85. That's how Bob interpretted it.

Apparently you'd interpret it as 43.75 * (1 + 0.10) = 43.75 * 1.1
48.125. If this is how you mean for y + x% to be interpetted, then yo
should make it clear that's what you mean. I know most calculators tha
have % keys work like this, but Excel doesn't, and you ask question
about Excel, you have to use Excel's conventions or be VERY CLEAR whic
alternative convention you're using.

To get back to your original problem, it's still just an algebrai
exercise.

(43.75+x%) -7.5% = 50.31

43.75 * (1 + x/100) * (1 - 0.075) = 50.31
1 + x/100 = 50.31 / (43.75 * (1 - 0.075))
x/100 = 50.31 / (43.75 * (1 - 0.075)) - 1
x = (50.31 / (43.75 * (1 - 0.075)) - 1) * 100 = 24.31814

so x% = 24.318% rounded to 5 digits

 

[mows]

Richard,

I'm trying to get x on one side of this equation (solve for x )so I can
enter it into excel but my math skills are poor.

(43.75+x%) -7.5% = 50.31

43.75, 7.5% or 7.5/100 and 50.31 exist in cells I've created so I need to
put the formula in a cell to solve for x.
Any help from you mathematicians would be appreciated.

...Hi Bob,
...Thanks for your reply but it's not correct.

Perhaps you are looking for solution to

(43.75 + 43.75 x /100) *(1-7.5/100) = 50.31
which turns out to be 24.3181467...

Let's generalise to
(n + n x / 100) * (1 - k / 100) = m, then
x = 10000 m / ((100 - k) n) - 100.

So, if A1 is 43.75, B1 is 50.31, C1 is 7.5, then
=10000*B1/((100-C1)*A1)-100

mows
Excel XP / WinXP

 

[Richard Ruda]

24.3xx is correct - thank you very much

 

[Dana DeLouis]

If you would like to keep your percentage of 7.5% in a cell (vs just 7.5),
you could adjust mows excellent formula to
=B1/(A1-A1*C1)-1

Dana