Cynthia invests some money in a bank which pays 5% compound interest per year. She wants it to be worth over £8000 at the end of 3 years. What is the smallest amount , to the nearest pound , she can invest?

Respuesta :

[tex]\bf \qquad \textit{Compound Interest Earned Amount}

\\\\

A=P\left(1+\frac{r}{n}\right)^{nt}

\quad

\begin{cases}

A=\textit{accumulated amount}\to &8000\\

P=\textit{original amount deposited}\\

r=rate\to 5\%\to \frac{5}{100}\to &0.05\\

n=

\begin{array}{llll}

\textit{times it compounds per year}\\

\textit{is only once, so}

\end{array}\to &1\\

t=years\to &3

\end{cases} [/tex]

[tex]\bf 8000=P\left(1+\frac{0.05}{1}\right)^{1\cdot 3}\implies 8000=P(1.05)^3\implies \cfrac{8000}{1.05^3}=P\\\\\\6910.70\approx P\implies  \stackrel{\textit{rounded up}}{6911 = P}\qquad  therefore\qquad 6911~~\leqslant ~~P[/tex]