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Question 1089487: Please help me solve this question: 
Found 2 solutions by Theo, MathTherapy:
Answer by Theo(13342)   (Show Source):
You can put this solution on YOUR website! Please help me solve this question:
Kurt opened a savings account by making an initial deposit of $30,000. If the account accrues an interest of 12% a year, in how many years will he double the money in his account?
your use of the brackets wasn't necessary and didn't result in what i'm sure you wanted because those brackets are used to show algebraic equations and anything has all spaces removed.
for example:
with brackets, the algebraic equation of y = log( ( x ) ) / ( x ^ 3 ) is shown as:
y = 
you can see that all the spaces are removed and the equation is put in a format that you might do if you manually showed the formula.
now to your problem.
Kurt opened a savings account by making an initial deposit of $30,000. If the account accrues an interest of 12% a year, in how many years will he double the money in his account?
the formula to use here is f = p * (1+r)^n
f is the future value
p is the present value
r is the interest rate per time period
n is the number of time periods.
your time periods are in years.
the formula becomes:
60,000 = 30,000 * (1 + .12) ^ n
you want to solve for n, so you will need to use logs.
divide both sides of the equation by 30,000 to get:
2 = (1 + .12) ^ n
simplify to get 2 = 1.12^n
take the log of both sides of the equation to get log(2) = log(1.12^n)
since log(a^b) = b*log(a), this becomes:
log(2) = n * log(1.12)
divide both sides of the equation by log(1.12) to get log(2)/log(1.12) = n
solve for n to get n = log(2)/log(1.12) = 6.116255374
them money will double in 6.116255374 years.
confirm as follows:
30,000 * 1.12 ^ 6.116255374 = 60,000
the solution looks good.
Answer by MathTherapy(10552)  (Show Source):
You can put this solution on YOUR website!
Please help me solve this question:
The amount doesn't matter at all.
In other words, ANY amount with annual compounding interest of 12% will DOUBLE in: 
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