# Thread: Help with exponential equation calculation

1. ## Help with exponential equation calculation

Hi i am trying to work out the following equation to get graph some theoretical results but think i am doing it incorrectly.

The equation is A = 100 x e^-(100 * exp-((σ*ppm * Na *l * 100)/(w * d * 10^6))

Now i am using excel so does the equation above equate to the expression below to work it out in excell?
A= 100 x EXP((-σ*ppm * Na *l * 100)/(w * d * 10^6))

My values are
σ = 1.34E-20
ppm = 100
Na = 6.023 x 10^24
l = 100cm
w = 26.037354
d = 911.8263883

The value i am getting is 71.18439629
which i think is wrong so either i am working out the equation incorrectly. I would just like to know if my calculations are being carried out correctly thanks
K

2. Originally Posted by k241
Hi i am trying to work out the following equation to get graph some theoretical results but think i am doing it incorrectly.

The equation is A = 100 x e^-(100 * exp-((σ*ppm * Na *l * 100)/(w * d * 10^6))

Now i am using excel so does the equation above equate to the expression below to work it out in excell?
A= 100 x EXP((-σ*ppm * Na *l * 100)/(w * d * 10^6))

My values are
σ = 1.34E-20
ppm = 100
Na = 6.023 x 10^24
l = 100cm
w = 26.037354
d = 911.8263883

The value i am getting is 71.18439629
which i think is wrong so either i am working out the equation incorrectly. I would just like to know if my calculations are being carried out correctly thanks
K
since your original eqiation contains two nested exponential functions, and your excel expression just one the excel expression is wrong.

RonL