Question 728803
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*[tex \LARGE \ \ \ \ \ \ \ \ \ \ A\ =\ P\left(1\ +\ \frac{r}{n}\right)^{nt}]


Where *[tex \LARGE A] is the future value, *[tex \LARGE P] is the present value, i.e. the starting principal, *[tex \LARGE r] is the interest rate as a decimal (the percentage divided by 100), *[tex \LARGE n] is the number of compounding periods per year, and *[tex \LARGE t] is the number of years.  Since you are compounding annually, *[tex \LARGE n\ =\ 1] and the formula reduces to:


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ A\ =\ P\left(1\ +\ r\right)^t]


Since you want the principal to quadruple, *[tex \LARGE \frac{A}{P}\ =\ 4] must be true, hence solve:


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ \left(1\ +\ 0.04\right)^t\ =\ 4]


for *[tex \LARGE t]


Hint: Take the log of both sides, any base -- it doesn't matter.  Then use:  *[tex \LARGE \log_b(x^a)\ =\ a\log_b(x)]


John
*[tex \LARGE e^{i\pi}\ +\ 1\ =\ 0]
<font face="Math1" size="+2">Egw to Beta kai to Sigma</font>
My calculator said it, I believe it, that settles it
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