To calculate the annual average change in Radu's mutual fund investment over the three years, we'll use the arithmetic mean. The arithmetic mean is calculated by summing up the percentages and then dividing by the number of years.

The formula is:

$\text{Average Change} = \frac{\text{Sum of Yearly Changes}}{\text{Number of Years}}$

Given the yearly changes:

• Year 1: 6.90%
• Year 2: -5.99%
• Year 3: -3.81%

Let's calculate the average change.The annual average change in Radu's investment is -0.97%, indicating a slight average decrease per year over the three years.

Would you like more details on the calculation or have any further questions? Here are some related questions to explore:

1. How would the average change differ if one year had a large positive return, like 20%?
2. What is the difference between arithmetic mean and geometric mean in the context of investment returns?
3. If Radu's investment increased by 10% in the fourth year, how would that impact the average?
4. What factors might explain the negative trend in Radu's mutual fund performance?
5. How does compounding affect long-term investment returns?

Tip: The arithmetic mean is useful for quick averages, but the geometric mean gives a better sense of compounded growth in investments over time.