Final answer:
To calculate the interest rate, you find the amount of interest earned by subtracting the initial investment from the final amount. Then use the simple interest formula to solve for the interest rate over the monthly period. The annual interest rate can be found and then converted to a monthly rate if needed.
Step-by-step explanation:
The student is asking how to calculate interest rate for an increase in investment over a period of a month. To find the monthly interest rate, we can use the formula for simple interest, which is Interest = Principal × Rate × Time.
To solve this, we first need to find the amount of interest earned which is the difference between the final amount and the initial principal. In this case, the interest earned is $73,543.03 - $73,248.97, which equals $294.06. The principal amount (initial investment) is $73,248.97, and since the growth happened over the course of a month, we'll consider the time factor as 1/12 (as one month is 1/12 of a year). Now we just need to solve the equation for the Rate, which is the unknown.
The equation becomes $294.06 = $73,248.97 × Rate × (1/12). Solving for Rate, we get Rate = (12 × $294.06) / $73,248.97, which gives us the annual interest rate. To find the monthly rate, we could directly solve with the monthly time factor, resulting in the same rate over the different time period.
Remember to convert the calculated annual rate to a percentage and round to the nearest tenth.