Calculating Compound Interest

Problema e solução em inglês, como no livro original.

If we invest $3,000 in an investment account paying 3% interest compounded quarterly, how much will the account be worth in 10 years?

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Solução
Because we are starting with $3,000, $P = 3000.$ Our interest rate is 3%, so $r =$ Because we are compounding quarterly, we are compounding 4 times per year, so $n = 4.$ We want to know the value of the account in 10 years, so we are looking for $A (10),$ the value when $t =$

$\begin{array}{l} A (t) & = P {(1 + \frac{r}{n})}^{n t} & Use the compound interest formula . \\ A (10) & = 3000 {(1 + \frac{0.03}{4})}^{4⋅10} \begin{matrix} \end{matrix} & Substitute using given values . \\ \approx $ 4045.05 & Round to two decimal places . \end{array}$
The account will be worth about $4,045.05 in 10 years.

Sua vez

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An initial investment of $100,000 at 12% interest is compounded weekly (use 52 weeks in a year). What will the investment be worth in 30 years?

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