To find the total amount in the account 20 years from today, we need to consider both the future value of Derek's deposits and the future value of the existing balance.
Step 1: Future Value of Existing Balance
Derek currently has $15,000 in the account. This amount will earn interest for 20 years. We can calculate the future value using the formula for compound interest:
\[ FV = PV(1 + r)^n \]
Where:
- \(FV\) = future value
- \(PV\) = present value ($15,000)
- \(r\) = annual interest rate (7% or 0.07)
- \(n\) = number of years (20)
Substituting the values into the formula:
\[ FV = 15000(1 + 0.07)^{20} \]
Calculating this:
\[ FV = 15000(1.07)^{20} \] \[ FV = 15000 \times 3.8697 \quad (\text{approximately, using a calculator}) \] \[ FV \approx 58045.50 \]
Step 2: Future Value of Annual Deposits
Derek will be making annual deposits of $5,000 for 15 years. Since the first deposit will be made next year, these deposits will not earn interest for the entirety of the 20 years. Instead, they will earn interest for a decreasing number of years (from 15 years down to 1 year).
The future value of a series of deposits can be calculated using the future value of an annuity formula:
\[ FV = P \times \frac{(1 + r)^n - 1}{r} \]
Where:
- \(P\) = annual deposit ($5,000)
- \(r\) = annual interest rate (0.07)
- \(n\) = number of deposits (15)
Substituting the values:
\[ FV = 5000 \times \frac{(1 + 0.07)^{15} - 1}{0.07} \]
Calculating this step-by-step:
- Calculate \((1 + 0.07)^{15}\):
\[ (1.07)^{15} \approx 2.7591 \quad (\text{approximately}) \]
- Subtract 1 from this result:
\[ 2.7591 - 1 = 1.7591 \]
- Divide by the interest rate:
\[ \frac{1.7591}{0.07} \approx 25.13 \quad (\text{approximately}) \]
- Multiply by the deposit amount:
\[ FV \approx 5000 \times 25.13 \approx 125656.52 \]
Step 3: Total Amount in the Account
Now we add the future value of the existing balance and the future value of the deposits:
\[ Total , FV = FV_{\text{existing}} + FV_{\text{deposits}} \] \[ Total , FV \approx 58045.50 + 125656.52 \approx 183702.02 \]
Final Result
The total amount in Derek's account 20 years from today will be approximately $183,702.02.