SOLUTION: I have tried this equation numerous times.. but I can't seem to get the time. Here is the problem : Find the time required for an investment of 5000 dollars to grow to 6400 dol

Algebra ->  Equations -> SOLUTION: I have tried this equation numerous times.. but I can't seem to get the time. Here is the problem : Find the time required for an investment of 5000 dollars to grow to 6400 dol      Log On


   

Question 193774: I have tried this equation numerous times.. but I can't seem to get the time. Here is the problem :
Find the time required for an investment of 5000 dollars to grow to 6400 dollars at an interest rate of 7.5 percent per year, compounded quarterly.
Here is what I have done:
6400=5000(1+(0.075/4))^4t
5000(1+(0.075/4))^4t=6400
5000(1+.01875)^4t=6400
5000/5000(1.01875)^4t=6400/5000
(1.01875)^4t=1.28
4t*ln(1.01875)=ln(1.28)
t=ln(1.28)/4*ln(1.01875)
Answer by Alan3354(69443) About Me  (Show Source):
You can put this solution on YOUR website!
I have tried this equation numerous times.. but I can't seem to get the time. Here is the problem :
Find the time required for an investment of 5000 dollars to grow to 6400 dollars at an interest rate of 7.5 percent per year, compounded quarterly.
Here is what I have done:
6400=5000(1+(0.075/4))^4t
5000(1+(0.075/4))^4t=6400
5000(1+.01875)^4t=6400
5000/5000(1.01875)^4t=6400/5000
(1.01875)^4t=1.28
4t*ln(1.01875)=ln(1.28)
t=ln(1.28)/4*ln(1.01875)
--------------------
r = 1.01875 per quarter
5000*1.01875^p = 6400 (p = periods)
1.01875^p = 1.28
p*log(1.01875) = log(1.28)
p = log(1.28)/log(1.01875)
p = 13.288 quarters
p = ~ 3.32 years