Math formula translation to Excel formula

[Charmwah]

Good afternoon all

Can anybody please help me translate the formula below into Excel speak:

[FONT=&quot]Answer = 10 log[10^(X1/10)+10^(X2/10)+10^(X3/10)]

Where X1, X2 & X3 are my data entry points. I have tried it as the following but the answer is not what I expect:

[/FONT]=LOG10(10^(X1/10)+10^(X2/10)+10^(X3/10))

Kind regards

Dave

 

[Rick Rothstein]

Can anybody please help me translate the formula below into Excel speak:

[FONT="]Answer = [B][COLOR="#008000"]10 [/COLOR][/B]log[10^(X1/10)+10^(X2/10)+10^(X3/10)]

Where X1, X2 & X3 are my data entry points. I have tried it as the following but the answer is not what I expect:

[/FONT]=10 * LOG10(10^(X1/10)+10^(X2/10)+10^(X3/10))

Maybe what I show in red (which assumes what I marked in green is supposed to be 10 times the log value). I am also assuming you were correct when you assumed "log" in your original formula meant "Log Base 10".

 

[cerfani]

i think he is just writing the base first and not multiplying (normally you would say Log10)

Just tell us what X1-3 equals and the expected result

 

[Charmwah]

i think he is just writing the base first and not multiplying (normally you would say Log10)

Just tell us what X1-3 equals and the expected result

Thanks Cerfani.

X1 = 26.9
X2 = 31.5
X3 = 28.2

Answer = 28

Kind regards

 

[cerfani]

I am getting 3.40875

10^2.69
+10^3.15
+10^2.82

=

~ 489.7788
+~1412.5375
+~660.6934

= ~2563.0098

Log10(~2563.0098) = 3.408750


10^3.408750 = 2563.0098

looks fine to me... you must have parentheses out of place

 

[Charmwah]

Hi Cerfani

I was getting that initially, but I changed my formula to the following:

=SUM(10*LOG(10^(X1/10)+10^(X2/10)+10^(X3/10)))

And I now get the answer of *34.09*.

This would seem closer to the figure i'm expecting...

 

[cerfani]

Hi Cerfani

I was getting that initially, but I changed my formula to the following:

=SUM(10*LOG(10^(X1/10)+10^(X2/10)+10^(X3/10)))

And I now get the answer of *34.09*.

This would seem closer to the figure i'm expecting...

Log function asks you to define base but if not it just uses 10... so you are doing the same thing just multiplying the result by ten (3.40875 * 10)

Perhaps you were using a different base to get 28?

if the base is ~1.323552 THEN you will get 28

 

[Charmwah]

Log function asks you to define base but if not it just uses 10... so you are doing the same thing just multiplying the result by ten (3.40875 * 10)

Perhaps you were using a different base to get 28?

if the base is ~1.323552 THEN you will get 28

Thanks Cerfani. I think the formula is sound, perhaps its the original answer which is at fault! Appreciate your help though =D

 

[cerfani]

ok no problem, hope that helped