$1000 is invested at 8% interest compounded annually. $80 in interest is earned in the first year. Knowing that compound interest grows exponentially, how much interest is earned in the second year? Include dollars and cents in your answer.

1 answer

To calculate the interest earned in the second year when $1000 is invested at an 8% interest rate compounded annually, we start with the following information:

  1. Principal (P): $1000
  2. Interest Rate (r): 8% (or 0.08 in decimal form)

In the first year, the interest earned is calculated as follows:

\[ \text{Interest for Year 1} = P \times r = 1000 \times 0.08 = 80 \]

This confirms that $80 in interest is indeed earned in the first year.

To find the total amount after the first year, we add the interest earned to the principal:

\[ \text{Total Amount after Year 1} = P + \text{Interest for Year 1} = 1000 + 80 = 1080 \]

In the second year, the interest is calculated on the new principal, which is the amount after the first year:

\[ \text{Principal for Year 2} = 1080 \]

Now, we will calculate the interest earned in the second year using the same interest rate:

\[ \text{Interest for Year 2} = \text{Principal for Year 2} \times r = 1080 \times 0.08 \]

Calculating that gives:

\[ \text{Interest for Year 2} = 1080 \times 0.08 = 86.4 \]

Therefore, the amount of interest earned in the second year is:

\[ \text{Interest for Year 2} = 86.40 \]

So, the final answer is:

\[ \boxed{86.40} \]