Car Cost Interest
1. **Problem Statement:** Jamie made a down payment of 1200 and monthly payments of 270 for 4 years and 8 months. The interest rate is 1.00% compounded quarterly. We need to find:
a. The cost of the car at purchase.
b. The total interest paid over the term.
2. **Given Data:**
- Down payment, $D = 1200$
- Monthly payment, $P = 270$
- Term: 4 years 8 months = $4 \times 12 + 8 = 56$ months
- Interest rate per quarter, $i_q = 1.00\% = 0.01$
3. **Convert interest rate to monthly rate:**
Since interest is compounded quarterly, the quarterly rate is 0.01.
Monthly rate $i_m$ is found by:
$$
i_m = (1 + i_q)^{1/3} - 1 = (1 + 0.01)^{1/3} - 1$$
Calculate:
$$
i_m = 1.01^{1/3} - 1 \approx 1.003322 - 1 = 0.003322$$
So monthly interest rate $i_m \approx 0.003322$ (or 0.3322%).
4. **Calculate the present value of the monthly payments:**
The monthly payments form an ordinary annuity. The present value $PV$ of these payments is:
$$
PV = P \times \frac{1 - (1 + i_m)^{-n}}{i_m}
$$
where $n = 56$ months.
Calculate:
$$
PV = 270 \times \frac{1 - (1 + 0.003322)^{-56}}{0.003322}
$$
First calculate $(1 + 0.003322)^{-56}$:
$$
(1.003322)^{-56} = \frac{1}{(1.003322)^{56}} \approx \frac{1}{1.204} = 0.8307
$$
Then:
$$
PV = 270 \times \frac{1 - 0.8307}{0.003322} = 270 \times \frac{0.1693}{0.003322} = 270 \times 50.97 = 13761.9
$$
5. **Calculate the total cost of the car:**
The total cost is the down payment plus the present value of the monthly payments:
$$
\text{Cost} = D + PV = 1200 + 13761.9 = 14961.9
$$
Rounded to nearest cent: 14961.90
6. **Calculate total amount paid:**
Total monthly payments:
$$
270 \times 56 = 15120
$$
Total amount paid including down payment:
$$
1200 + 15120 = 16320
$$
7. **Calculate total interest paid:**
Interest paid is total amount paid minus the cost of the car:
$$
\text{Interest} = 16320 - 14961.9 = 1358.1
$$
Rounded to nearest cent: 1358.10
**Final answers:**
a. Cost of the car = 14961.90
b. Total interest paid = 1358.10