\( \$ 1000 \) 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 \( \$ 2500 \) ? \[ \mathrm{t}=[\text { ? ] years } \]
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To find out how many years 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 \( t \), - \( P \) is the principal amount (the initial deposit or investment), - \( r \) is the annual interest rate (decimal), - \( e \) is the base of the natural logarithm (approximately equal to 2.71828), - \( t \) is the number of years the money is invested or borrowed for. Plugging in the given values into the formula we have: \[ 2500 = 1000 e^{0.07t} \] Dividing both sides by 1000: \[ 2.5 = e^{0.07t} \] Now we take the natural logarithm (ln) of both sides: \[ \ln(2.5) = 0.07t \] Now, solve for \( t \): \[ t = \frac{\ln(2.5)}{0.07} \] Calculating \( \ln(2.5) \): \[ \ln(2.5) \approx 0.9163 \] Now, substituting back: \[ t = \frac{0.9163}{0.07} \approx 13.09 \] Therefore, the money was in the bank for approximately \( 13.09 \) years. \[ \mathrm{t} \approx 13.1 \text{ years} \]