House Payment
1. **Stating the problem:**
We want to find the monthly payment that the parents will receive if the house is sold in 7 years for 3.2 million, with an interest rate of 8.06% compounded monthly.
Then, we need to find how many siblings must pay the monthly amount of 6700 each to reach this goal.
Finally, if only 3 children pay 6700 monthly, determine the future value they can accumulate in 7 years.
2. **Calculate the monthly interest rate:**
$$ i = \frac{8.06\%}{12} = 0.0806 / 12 = 0.006717 $$
3. **Calculate the total number of payments:**
$$ n = 7 \times 12 = 84 $$
4. **Find the monthly payment $P$ needed to accumulate $3,200,000$ in 7 years at monthly interest $i$ and $n$ payments using the future value of an annuity formula:**
$$ FV = P \times \frac{(1+i)^n - 1}{i} $$
Rearranged for $P$:
$$ P = FV \times \frac{i}{(1+i)^n - 1} $$
Plug in values:
$$ P = 3200000 \times \frac{0.006717}{(1+0.006717)^{84} - 1} $$
Calculate $(1+0.006717)^{84}$:
$$ (1.006717)^{84} \approx 1.747 $$
Calculate denominator:
$$ 1.747 - 1 = 0.747 $$
Calculate numerator:
$$ 3200000 \times 0.006717 = 21494.4 $$
Calculate $P$:
$$ P = \frac{21494.4}{0.747} \approx 28775.36 $$
So, the parents receive roughly $28775.36$ per month total.
5. **Calculate the number of siblings needed if each can pay $6700$ per month:**
$$ \text{siblings} = \frac{28775.36}{6700} \approx 4.29 $$
Since siblings must be a whole number and meet or exceed this, the answer is 5 siblings.
6. **Calculate how much 3 children paying $6700$ monthly can accumulate in 7 years:**
Total monthly payment from 3 children:
$$ 3 \times 6700 = 20100 $$
Use future value of annuity formula:
$$ FV = P \times \frac{(1+i)^n - 1}{i} $$
Already know:
$$ (1+i)^n - 1 = 0.747,\quad i=0.006717 $$
Calculate $FV$:
$$ FV = 20100 \times \frac{0.747}{0.006717} = 20100 \times 111.257 \approx 2236493 $$
**Final answers:**
- Parents receive about $28775.36$ per month total.
- Exactly $5$ siblings needed paying $6700$ each.
- Three siblings paying $6700$ each can offer about $2,236,493$ after 7 years.