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If the daily exponential decay is 3%, how many days will it take for the amount to be reduced to 4% of the original?

 Oct 9, 2015
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If the daily exponential decay is 3%, how many days will it take for the amount to be reduced to 4% of the original?

 

Hi Saintcyr :)

 

let the initial amount be X, let n be the number of days that have past.

 

end of day n           A=X*0.97^n  

 

When will       A=0.04X

 

0.04X=X*0.97^n

0.04 = 0.96^n

log 0.04 = log 0.97^n

log 0.04 = nlog 0.97

n=log0.04/log0.97

n=105.7

so after 105.7 days there will be 4% remaining

so after 106 days there will be less than 4% remaining.

 Oct 9, 2015
edited by Melody  Oct 9, 2015

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