Questions: An initial investment amount P, an annual interest rate r, and a time t are given. Find the future the doubling time T for the given interest rate.
P= 450, r=2.35%, t=12 yr
Transcript text: An initial investment amount $P$, an annual interest rate $r$, and a time $t$ are given. Find the futur the doubling time T for the given interest rate.
\[
P=\$ 450, r=2.35 \%, t=12 \mathrm{yr}
\]
Solution
Solution Steps
To find the future value of an investment with compound interest, we use the formula \( A = P(1 + \frac{r}{100})^t \). To find the doubling time \( T \), we use the rule of 70, which is an approximation given by \( T \approx \frac{70}{r} \).
Step 1: Calculate Future Value
To find the future value \( A \) of the investment after \( t = 12 \) years, we use the formula for compound interest:
\[
A = P \left(1 + \frac{r}{100}\right)^t
\]
Substituting the given values \( P = 450 \), \( r = 2.35 \), and \( t = 12 \):
\[
A = 450 \left(1 + \frac{2.35}{100}\right)^{12} \approx 594.6572
\]
Step 2: Calculate Doubling Time
To find the doubling time \( T \) for the given interest rate, we can use the rule of 70:
\[
T \approx \frac{70}{r}
\]
Substituting \( r = 2.35 \):
\[
T \approx \frac{70}{2.35} \approx 29.7872
\]
Final Answer
The future value of the investment after 12 years is approximately \( A \approx 594.6572 \) and the doubling time is approximately \( T \approx 29.7872 \).
Thus, the final answers are:
\[
\boxed{A \approx 594.6572}
\]
\[
\boxed{T \approx 29.7872}
\]