How much money invested at 5% compounded continuously for 3 years will result in $820?

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The formula to calculate the future value (A) of an investment compounded continuously is given by:

A = P * e^(rt)

Where:
A = Future value
P = Principal amount (initial investment)
e = Euler's number (approximately 2.71828)
r = Annual interest rate (as a decimal)
t = Time period in years

In this case, we have the following information:
A = $820
r = 5% = 0.05
t = 3 years

Let's plug in the values and solve for P:

820 = P * e^(0.05 * 3)

Divide both sides of the equation by e^(0.05 * 3):

820 / e^(0.05 * 3) = P

Using a calculator, we can find:
e^(0.05 * 3) ≈ 1.15763

Substituting this value back into the equation:

820 / 1.15763 = P

P ≈ $709.99

Therefore, approximately $709.99 needs to be invested at 5% compounded continuously for 3 years to result in $820.