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Understanding Effective Interest Rates

May 7, 2025

Lecture on Financial Mathematics: Effective Rate Interest Formula

Presenter

  • Zo Li from Bright Young Brains

Topic

  • Financial Mathematics: Using the Effective Rate Interest Formula

Key Concepts

  • Nominal Rate (I_Norm): The stated interest rate on a loan before taking into account compounding.
    • In the example provided, I_Norm is 13%.
  • Compounding Frequency (M): How often the interest is compounded over a period.
    • In the example provided, the interest is compounded monthly, thus M = 12.

Problem Statement

  • John purchased a car and received a loan from the bank.
  • The loan had a nominal rate of 13% per annum, compounded monthly.
  • Objective: Calculate the effective annual interest rate.

Effective Rate Interest Formula

  • Formula: Involves converting nominal interest rate to effective interest rate considering the frequency of compounding.

Steps to Solve

  1. Identify given values:
    • I_Norm = 13%
    • M = 12 (since compounding is monthly)
  2. Convert I_Norm to decimal if necessary:
    • 13% as a decimal is 0.13 or 13/100.
  3. Use the effective rate interest formula:
    • Plug in the values for I_Norm and M.
  4. Calculation:
    • Compute using a calculator.
    • Write results to four decimal places.
    • Multiply by 100 to convert the result into a percentage.

Conclusion

  • Understanding how to apply the effective rate interest formula helps in determining the real cost of borrowing or the real return on investments.

Additional Resources

  • View more videos in the playlist for similar problems and solutions.