Jackie deposits 325 dollars in an account that pays 4.1% interest compounded annually. How much money will Jackie have in her account after 3 years?

Difficulty: Medium

Correct Answer: 366.64 dollars

Explanation:


Introduction:
This question is another example of compound interest with annual compounding, but with a rate that includes a decimal (4.1%). It demonstrates how to handle non integer rates and exponentiation over 3 years to find the final account balance.


Given Data / Assumptions:

  • Principal P = 325 dollars
  • Annual interest rate r = 4.1% per annum
  • Compounded annually
  • Time t = 3 years
  • We need the total amount after 3 years


Concept / Approach:
With annual compounding, we use:
A = P * (1 + r/100)^tHere, r = 4.1 and t = 3. The interest is added once at the end of each year, and the amount grows multiplicatively.


Step-by-Step Solution:
Step 1: Convert the rate to growth factor.1 + r/100 = 1 + 4.1 / 100 = 1 + 0.041 = 1.041Step 2: Compute the cube of 1.041.(1.041)^3 ≈ 1.128275Step 3: Apply the formula.A = 325 * (1.041)^3A ≈ 325 * 1.128275 ≈ 366.64 dollarsThus, Jackie will have about 366.64 dollars after 3 years.


Verification / Alternative check:
We can approximate year by year:
End of year 1: 325 + 4.1% of 325 ≈ 325 + 13.33 = 338.33 dollarsEnd of year 2: 338.33 + 4.1% of 338.33 ≈ 338.33 + 13.87 ≈ 352.20 dollarsEnd of year 3: 352.20 + 4.1% of 352.20 ≈ 352.20 + 14.44 ≈ 366.64 dollarsThis sequential calculation matches the formula based result, confirming the answer.


Why Other Options Are Wrong:

  • 346.64 and 356.64 dollars: These values are lower than the correct compound amount and reflect underestimation of interest in later years.
  • 376.64 dollars: Slightly higher than correct, from over rounding or increasing interest at each step too much.
  • 360 dollars: Rough estimate without exact compounding.


Common Pitfalls:
Errors often come from incorrect exponentiation of 1.041 or using simple interest instead of compounding. Some students mistakenly multiply 4.1% by 3 and add that, which would give only simple interest and a different result.


Final Answer:
Jackie will have approximately 366.64 dollars in her account after 3 years.

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