Annuity Balance
1. **State the problem:** Janet saves 500 at the beginning of every month for 15 years in a fund with an annual interest rate of 4.75% compounded annually. We need to find the balance at the end of 15 years and the interest earned.
2. **Identify the type of problem:** This is an annuity problem with monthly payments but interest compounded annually. We assume payments accumulate without interest during the year and interest is applied once per year.
3. **Calculate total number of payments:**
$$n = 15 \times 12 = 180 \text{ payments}$$
4. **Calculate the future value of the annuity:** Since interest is compounded annually, we consider yearly contributions. Total yearly contribution:
$$500 \times 12 = 6000$$
5. **Use the future value of an ordinary annuity formula for yearly contributions:**
$$FV = P \times \frac{(1 + r)^t - 1}{r}$$
where
$P = 6000$ (annual payment),
$r = 0.0475$ (annual interest rate),
$t = 15$ years.
6. **Calculate:**
$$FV = 6000 \times \frac{(1 + 0.0475)^{15} - 1}{0.0475}$$
Calculate $(1 + 0.0475)^{15}$:
$$1.0475^{15} \approx 2.0006$$
So,
$$FV = 6000 \times \frac{2.0006 - 1}{0.0475} = 6000 \times \frac{1.0006}{0.0475} \approx 6000 \times 21.06 = 126360$$
7. **Calculate total amount saved without interest:**
$$Total\,payments = 500 \times 180 = 90000$$
8. **Calculate interest earned:**
$$Interest = FV - Total\,payments = 126360 - 90000 = 36360$$
9. **Round to nearest cent:**
Balance: 126360.00
Interest earned: 36360.00
**Final answers:**
- Balance at end: $126360.00$
- Interest earned: $36360.00$