1. **State the problem:** Find the principal amount $P$ that will grow to a future value $A = 8104.00$ at a simple interest rate of 7.8% per year over 2 months.
2. **Formula for simple interest:**
$$A = P(1 + rt)$$
where $A$ is the future value, $P$ is the principal, $r$ is the annual interest rate (in decimal), and $t$ is the time in years.
3. **Convert given values:**
- Interest rate: $r = 7.8\% = 0.078$
- Time: $t = \frac{2}{12} = 0.166667$ years
- Future value: $A = 8104.00$
4. **Rearrange formula to solve for $P$:**
$$P = \frac{A}{1 + rt}$$
5. **Substitute values:**
$$P = \frac{8104.00}{1 + 0.078 \times 0.166667}$$
6. **Calculate denominator:**
$$1 + 0.078 \times 0.166667 = 1 + 0.013000 = 1.013000$$
7. **Calculate principal:**
$$P = \frac{8104.00}{1.013000}$$
8. **Show cancellation step:**
$$P = \frac{\cancel{8104.00}}{\cancel{1.013000}}$$
9. **Final calculation:**
$$P \approx 7999.21$$
**Answer:** The principal is approximately **7999.21**.
Simple Interest B2C9A6
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