Question 18 • Mathematics III
Use the compound interest formula with principal $1,900, annual rate 0.04, and 2 compounding periods per year: 3,875.79 = 1,900(1.02)^(2t). Dividing by 1,900 gives approximately 2.0399 = (1.02)^(2t), which is about 36 semiannual compounding periods. Since there are 2 periods per year, 36 ÷ 2 = 18 years, so the correct choice is 18 years.
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