The Solution:
Given:
[tex]\begin{gathered} P=\text{ \$}55000 \\ r=7.5\text{ \% compounded quarterly}=\frac{7.5}{400}=0.01875 \\ t=5\text{ years}=5\times4=20\text{ periods} \end{gathered}[/tex]
Required:
Find the value of the investment after 5 years.
The Formula:
[tex]V=P(1+\frac{r}{n})^{nt}[/tex]
In this case,
[tex]\begin{gathered} V=Value\text{ of the investment}=? \\ P=\text{ \$55000} \\ r=0.075 \\ n=\text{ number of periods in a year}=4 \\ t=5\text{ years} \end{gathered}[/tex]
Substitute:
[tex]V=55000(1+\frac{0.075}{4})^{(5\times4)}[/tex][tex]V=55000(1+0.01875)^{20}=55000(1.01875)^{20}[/tex][tex]V=79747.1414\approx\text{ \$}79747.14[/tex]
Answer:
(a) $79,747.14
Find the number of months it will take the account to increase to more than $70,000
Solve for n in the equation below:
[tex]55000(1.01875)^n>70000[/tex][tex]\begin{gathered} (1.01875)^n>\frac{70000}{55000} \\ \\ (1.01875)^n>\frac{14}{11} \end{gathered}[/tex][tex]ln(1.01875)^n>ln(\frac{14}{11})[/tex][tex]n=\frac{ln(\frac{14}{11})}{ln(1.01875)}>12.982\approx13\text{ months}[/tex]
Answer:
13 months or more