Question: You currently have $6,184.50 in an account that pays 9.06% annual interest. You plan to deposit in this account $8,495.32 at the BEGINNING of each year until the account reaches $98,758.82. How many months will it take for you to reach your goal? Enter your answer to two decimal places.
1. **State the problem:**
You have an initial amount $P = 6184.50$ in an account with an annual interest rate $r = 9.06\% = 0.0906$. You plan to deposit $D = 8495.32$ at the beginning of each year. You want to find the time $t$ in months for the account balance to reach $A = 98758.82$.
2. **Formula used:**
Since deposits are made at the beginning of each year, this is an annuity due problem with initial principal. The future value $A$ after $n$ years is given by:
$$
A = P(1+r)^n + D \times \frac{(1+r)^n - 1}{r} \times (1+r)
$$
where $n$ is the number of years.
3. **Rewrite the formula to solve for $n$:**
Let $x = (1+r)^n$. Then:
$$
A = P x + D \times \frac{x - 1}{r} \times (1+r)
$$
Multiply both sides by $r$ to clear denominator:
$$
r A = r P x + D (x - 1)(1+r)
$$
Expand right side:
$$
r A = r P x + D (1+r) x - D (1+r)
$$
Group terms with $x$:
$$
r A + D (1+r) = x (r P + D (1+r))
$$
Solve for $x$:
$$
x = \frac{r A + D (1+r)}{r P + D (1+r)}
$$
4. **Calculate $x$ numerically:**
$$
r = 0.0906, \quad P = 6184.50, \quad D = 8495.32, \quad A = 98758.82, \quad 1+r = 1.0906
$$
Calculate numerator:
$$
r A + D (1+r) = 0.0906 \times 98758.82 + 8495.32 \times 1.0906 = 8947.77 + 9265.88 = 18213.65
$$
Calculate denominator:
$$
r P + D (1+r) = 0.0906 \times 6184.50 + 8495.32 \times 1.0906 = 560.11 + 9265.88 = 9825.99
$$
So:
$$
x = \frac{18213.65}{9825.99} = 1.8549
$$
5. **Solve for $n$:**
$$
x = (1+r)^n \Rightarrow n = \frac{\ln(x)}{\ln(1+r)} = \frac{\ln(1.8549)}{\ln(1.0906)}
$$
Calculate:
$$
\ln(1.8549) = 0.6181, \quad \ln(1.0906) = 0.0867
$$
Therefore:
$$
n = \frac{0.6181}{0.0867} = 7.13 \text{ years}
$$
6. **Convert years to months:**
$$
\text{months} = 7.13 \times 12 = 85.56 \text{ months}
$$
**Final answer:** It will take approximately **85.56 months** to reach your goal.