\( \$ 1000 \) were deposited into an account with a \( 7 \% \) interest rate, compounded continuously. How many years was it in the bank if the current amount is \( \$ 2500 \) ? \[ \mathrm{t}=[?] \text { years } \] Round to the nearest year.
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The Deep Dive
To find out how long the money was in the bank, we can use the formula for continuous compounding, which is given by: \[ A = Pe^{rt} \] Where: - \( A \) is the amount of money accumulated after time \( t \) (the current amount), - \( P \) is the principal amount (the initial deposit), - \( r \) is the annual interest rate (decimal), - \( t \) is the time in years, - \( e \) is the base of the natural logarithm, approximately equal to 2.71828. Given: - \( A = 2500 \) - \( P = 1000 \) - \( r = 0.07 \) We can rearrange the formula to solve for \( t \): \[ 2500 = 1000 e^{0.07t} \] Divide both sides by 1000: \[ 2.5 = e^{0.07t} \] Now, take the natural logarithm of both sides: \[ \ln(2.5) = 0.07t \] Now, solve for \( t \): \[ t = \frac{\ln(2.5)}{0.07} \] Calculating the values: \[ t \approx \frac{0.9163}{0.07} \approx 13.09 \] Rounding to the nearest year, the time \( t \) is approximately: \[ \mathrm{t} = 13 \text{ years} \]