Ida is 25 years old and invests a one-time lump sum of $10,000 in her company's 401(k), which earns an average annual return of 6% compounded annually.Using the Rule of 72, about how many years will it take for Ida's investment to double?

The Rule of 72 estimates doubling time by dividing 72 by the annual return rate. At 6% per year, 72 ÷ 6 = 12 years. So it will take about 12 years for Ida’s investment to double, which is choice D.

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