8. laura is saving for college. she earned $450 in interest on her initial deposit of $1,000 on a 60 - month…

Explanation:

Step1: Convert time to years

Since there are 12 months in a year, for 60 - month investment, (t=\frac{60}{12}=5) years.

Step2: Use the simple - interest formula (I = Prt)

The simple - interest formula is (I = Prt), where (I) is the interest, (P) is the principal amount, (r) is the interest rate, and (t) is the time. We need to solve for (r). Rearranging the formula for (r), we get (r=\frac{I}{Pt}). Given (I = 450), (P = 1000), and (t = 5). Substitute these values into the formula: (r=\frac{450}{1000\times5}).

Step3: Calculate the value of (r)

First, calculate the denominator (1000\times5 = 5000). Then (r=\frac{450}{5000}=0.09)

Answer:

The simple - interest rate (r = 9%)