To determine the rate of an investment, we can use the formula for simple interest, given as:

$I = P \times r \times t$

Where:

• $I$ is the interest earned (which is 2,520),
• $P$ is the principal (initial investment, 10,500),
• $r$ is the rate (which we need to find),
• $t$ is the time (4 years).

Rearranging the formula to solve for $r$:

$r = \frac{I}{P \times t}$

Substituting the given values:

$r = \frac{2520}{10500 \times 4}$

Now let's calculate the value.The rate of the investment is $6\%$ per year.

Would you like more details or have any further questions? Here are five related questions you might consider:

1. How would this change if the interest was compounded annually?
2. What would the interest be for different time periods, such as 5 or 6 years?
3. How can we calculate the final amount using compound interest instead of simple interest?
4. If the principal was higher or lower, how would it affect the interest earned?
5. How do different interest rates affect the total return on an investment over time?

Tip: Simple interest grows linearly, while compound interest grows exponentially over time!