If you invest $8,600 at a 3.95% simple annual interest rate, approximately how long will it take for you to have a total of $21,000?

For simple interest, use A = P(1 + rt), where A is the final amount and P is the initial investment. Solving for time gives t = (A/P − 1)/r = (21,000/8,600 − 1)/0.0395 ≈ 36.5 years, so the best answer is 36.5 years.

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