Question:
Sam is carrying a 2 gallon bucket of milk to his house from the barn, which is 3 miles away from his house. However, the bucket has a leak in it. For each mile he walks, there is $\frac{2}{3}$ as much milk in the bucket as at the beginning of the mile. How many gallons of milk will be in the bucket when Sam gets home?

Answer:
At the end of the first mile, there will be $\frac{2}{3}$ of the initial milk in the bucket. Each additional mile multiplies this amount by $\frac{2}{3}$. Thus, when he arrives at home at the end of the third mile, there will be $\frac{2}{3} \cdot \frac{2}{3} \cdot \frac{2}{3} = \left(\frac{2}{3}\right)^{3}$ as much milk in the bucket. Since he had 2 gallons initially, the amount in the bucket when he gets home is $2 \cdot \left(\frac{2}{3}\right)^{3}$. Because $\left(\frac{a}{b}\right)^{n} = \frac{a^{n}}{b^{n}}$, this expression is equivalent to $2 \cdot \frac{2^{3}}{3^{3}}$. Because $n^{a} \cdot n^{b} = n^{a+b}$, this equals $\frac{2^{4}}{3^{3}}$. Multiplying the exponents out, we get $\boxed{\frac{16}{27}}$ gallons.