Question 301425
    How long does it take $1,150 to double if it is invested at 9% interest compounded monthly? Round your answer to the nearest tenth.
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Compound interest formula:
Regular Compound Interest Formula

{{{A = P(1+r/n)^(nt)}}}
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P = principal amount (the initial amount you borrow or deposit)
r  = annual rate of interest (as a decimal)
t  = number of years the amount is deposited or borrowed for.
A = amount of money accumulated after n years, including interest.
n  =  number of times the interest is compounded per year  
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{{{2(1150) = 1150(1+.09/12)^(12t)}}}
{{{2 = (1+.09/12)^(12t)}}}
{{{2 = (1.0075)^(12t)}}}
{{{log(1.0075,2) = 12t }}}
{{{log(2)/log(1.0075) = 12t }}}
{{{(log(2)/log(1.0075))/12 = t }}}
7.7 years = t