Compound Interest 64Ab7D
1. **State the problem:**
Brayden invests 400 at 9.25% interest compounded continuously.
William invests 400 at 8.875% interest compounded monthly.
We want to find how much Brayden has when William's money triples.
2. **Formulas:**
- Continuous compounding: $$A = P e^{rt}$$
- Monthly compounding: $$A = P \left(1 + \frac{r}{n}\right)^{nt}$$ where $n=12$ for monthly.
3. **Find time $t$ when William's money triples:**
$$3 \times 400 = 400 \left(1 + \frac{0.08875}{12}\right)^{12t}$$
Simplify:
$$3 = \left(1 + \frac{0.08875}{12}\right)^{12t}$$
Take natural log:
$$\ln(3) = 12t \ln\left(1 + \frac{0.08875}{12}\right)$$
Solve for $t$:
$$t = \frac{\ln(3)}{12 \ln\left(1 + \frac{0.08875}{12}\right)}$$
Calculate:
$$1 + \frac{0.08875}{12} = 1 + 0.0073958333 = 1.0073958333$$
$$\ln(3) \approx 1.098612$$
$$\ln(1.0073958333) \approx 0.007368$$
$$t = \frac{1.098612}{12 \times 0.007368} = \frac{1.098612}{0.088416} \approx 12.42 \text{ years}$$
4. **Calculate Brayden's amount at $t=12.42$ years:**
$$A = 400 e^{0.0925 \times 12.42}$$
Calculate exponent:
$$0.0925 \times 12.42 = 1.14885$$
Calculate:
$$A = 400 e^{1.14885}$$
$$e^{1.14885} \approx 3.154$$
$$A = 400 \times 3.154 = 1261.6$$
5. **Final answer:**
Brayden will have approximately **1262** dollars when William's money has tripled.