Re: Sarah invested $\$ 38,700$ in an account that paid 6.2 % annual int
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08 Feb 2026, 08:36
1. Identify the Variables
- Principal ( $P$ ):$ 38,700
- Annual Interest Rate $(r): 6.2 %=0.062$
- Compounding frequency ( $n$ ): 12 (monthly)
- Monthly Interest Rate $\((i): r / n=0.062 / 12 \approx 0.0051667\)$
- Total Time: 3 years $=36$ months.
2. Find the Balance at the Start of the Last Month
The interest for the 36th month is calculated based on the balance accumulated by the end of the 35th month. We use the compound interest formula:
$$
\(A=P\left(1+\frac{r}{n}\right)^{n t}\)
$$
For 35 months:
$$
\(\begin{gathered}
A_{35}=38,700 \times\left(1+\frac{0.062}{12}\right)^{35} \\
A_{35} \approx 38,700 \times(1.0051667)^{35} \\
A_{35} \approx 38,700 \times 1.19765 \approx \$ 46,349.36
\end{gathered}\)
$$
3. Calculate Interest for Month 36
Now, we apply the monthly interest rate to this balance:
$$
\(\begin{gathered}
\text { Interest }_{36}=\text { Balance }_{35} \times i \\
\text { Interest }_{36}=46,349.36 \times\left(\frac{0.062}{12}\right) \\
\text { Interest }_{36} \approx 46,349.36 \times 0.0051667 \approx \$ 239.47
\end{gathered}\)
$$