Question 5 • Financial Math
Use the compound-interest equation A = P(1 + r/n)^(nx). Here, 21,286.61 = 18,000(1 + 0.042/12)^(12x). Solving gives x = ln(21,286.61/18,000) ÷ [12 ln(1 + 0.042/12)] ≈ 4 years, so the correct choice is 4 years.
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