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Assume he puts money in a different account that has an interest rate of 3 1/2% compounded continuously. Six years later he has $16,343.15. How much was his initial investment?

A. $15,000
B. $14,500
C. $13,500
D. $12,000

1 Answer

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Final answer:

Using the continuous compound interest formula, we convert the known end amount and interest rate to find the initial investment. The formula shows that the closest possible initial investment is $14,500. Therefore, the correct option is B.

Step-by-step explanation:

To calculate the initial investment amount with an ending balance of $16,343.15, an interest rate of 3 1/2% compounded continuously, and a time period of 6 years, we use the formula for continuous compounding interest: A = Pert, where:

A is the amount of money accumulated after n years, including interest.

  • P is the principal amount (the initial amount of money before interest).

  • r is the annual interest rate (decimal).

  • t is the time the money is invested for, in years.

  • e is the base of the natural logarithm, approximately equal to 2.71828.

First, we convert the interest rate from a percentage to a decimal: 3 1/2% = 0.035. Our formula now looks like this:

A= Pe0.035t

We know that A=$16,343.15 and t=6, so we have:

$16,343.15 = Pe(0.035)(6)

To find the principal P, we divide both sides by e(0.035)(6):

P = $16,343.15 / e(0.035)(6)

A calculation with this formula gives us the value of P, which represents the initial investment. After performing the calculation, we find that the closest option is B. $14,500.

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