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Ryan
Ryan, Engineer
Category: Calculus and Above
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Experience:  B.S. in Civil Engineering
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Need help with an exponential formula. Given the following

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Need help with an exponential formula. Given the following statement with the min and max values...min:{
A: 200,
B: 2400
}
max:{
A: 2500
B: 75
}How do I calculated the value of B, with a specifc value of A ( between 200 and 2500 ). So to summarise with an example, if B = 1459, what formula can I use to get the value of A?

Hi,

Thank you for using the site. I'll be happy to help you with this problem.

I'll have a solution posted for you shortly.

Thanks,

Ryan

Hi again,

Here is a link to the solution:

Exponential

Please feel free to ask if you have any questions about this solution, and please let me know if you have any trouble accessing the file at that link.

Thanks,

Ryan

Customer: replied 4 years ago.
Thank you that looks great, will look in detail at it tomorrow and I'm sure mark it as solved.

You're quite welcome.

Customer: replied 4 years ago.
Hi, ok thank you for the very clear answer. What if I had a value for A and wanted to find B? Or do I need to post this as another question?
Customer: replied 4 years ago.
Sorry, it's late...correct me if I'm wrong but I think you already answered that in your calculations...(incorrect format but ) B=3239.66e -0.0015A

Then you would use the first formula:

B = 3239.66 * e^(-0.0015 * A)

So, if you had A = 531.81, you would get:

B = (3239.66)*e^(-0.0015 * 531.81)

B = (3239.66)*e^(-0.7977)

B = (3239.66)(0.4504)

B = 1459

Either formula will work both ways. It's just that if you have A and want B, you would use the above formula. And if you have B and want A, you would use the second one.

No need to apologize, by the way. I'm happy to help.

Customer: replied 4 years ago.
Ok, one more question, after which I'll be rating your response excellent.
I need the formula for some code so I need to convert B = 3239.66 * e^(-0.0015 * A) into Javascript. My Maths is very poor, am I correct the 'e^' is the symbol for exponential ( can I use 2.71828? ). So in non-mathematical longhand it's...
B= 3239.66 * ( 2.71828 * ( -0.0015 * A ) )
Thanks

Not exactly, since the (-0.0015 * A) part is an exponent, and not a factor.

You can do something like this in Javascript:

B = 3239.66 * math.exp(-0.0015 * A)

Alternatively (but equivalently), you could use:

B = 3239.66 * math.pow(2.71828, -0.0015 * A)

Ryan and other Calculus and Above Specialists are ready to help you
Customer: replied 4 years ago.
Many thanks.

You're very welcome. I'm glad that I could help.

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