Interest rate (with changing years). Keiko is looking at the following investment choices and wants to know what annual rate of return each choice produces. a. Invest \( \$ 450.00 \) and receive \( \$ 746.23 \) in 11 years. b. Invest \( \$ 3,600.00 \) and receive \( \$ 10,465.82 \) in 17 years. c. Invest \( \$ 32,914.85 \) and receive \( \$ 120,000.00 \) in 20 years. d. Invest \( \$ 33,619.78 \) and receive \( \$ 1,300,000.00 \) in 40 years. c. What annual rate of reth will Keiko earn if she invests \( \$ 32,914.85 \) today and receives \( \$ 120,000.00 \) in 20 years? \% (Round to two decimal places.)
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The Deep Dive
To determine the annual rate of return for Keiko's investment, we can use the formula for compound interest: \[ A = P(1 + r)^n \] Where: - \( A \) is the amount of money accumulated after n years, including interest. - \( P \) is the principal amount (the initial investment). - \( r \) is the annual interest rate (decimal). - \( n \) is the number of years the money is invested. Rearranging this formula to find \( r \): \[ r = \left( \frac{A}{P} \right)^{\frac{1}{n}} - 1 \] For option (c): - \( A = 120,000.00 \) - \( P = 32,914.85 \) - \( n = 20 \) Now plug in the numbers: \[ r = \left( \frac{120,000.00}{32,914.85} \right)^{\frac{1}{20}} - 1 \] Calculating the fraction: \[ \frac{120,000.00}{32,914.85} \approx 3.644 \] Then, apply the exponent: \[ r \approx (3.644)^{\frac{1}{20}} - 1 \approx 0.0810 \] Converting this to a percentage and rounding to two decimal places: \[ r \approx 8.10\% \] So, if Keiko invests \( \$ 32,914.85 \) today, she will earn an approximate annual rate of return of **8.10%** over the next 20 years.