SOLUTION: I need help solving this word problem: The debt on a certain credit card follows the function d=9000*1.015^t where d = debt in $ and t= time in months. A)How much debt will be

Question 115033: I need help solving this word problem:
The debt on a certain credit card follows the function d=9000*1.015^t where d = debt in $ and t= time in months.
A)How much debt will be owed in t=6 months?
B)How long will it take for debt to exceed $15,000?
I think i have A) here is what i did on it:
d=9000*1.015^6
d=$9,840.99
And i couldnt finish b part but here is where i got:
$15,000=9,000*1.015^t
6,000=1.015^t
I just dont understand how to get the t down from an exponent and finsih it for t!

Any help is greatly appreciated THANKS!
Answer by scott8148(6628) (Show Source): You can put this solution on YOUR website!
$15,000=9,000*1.015^t ___ DIVIDING by 9000 gives 5/3=1.015^t

taking the logarithm gives log(5/3)=t*log(1.015) ___ (log(5/3))/(log(1.015))=t
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