3. Throw a die three times, find the probability of getting exactly two ones.



The above text is translated into English, keeping the original text's line breaks and format.
$\begin{array}{l}\text { (Answer: } P=\frac{\mathrm{C}_{3}^{2} \cdot \mathrm{C}_{5}^{1}}{6^{3}}=\frac{5}{72} \text {. } \\ \text { Or } \mathrm{P}=\mathrm{C}_{3}^{2} \cdot\left(\frac{1}{6}\right)^{2} \cdot\left(\frac{5}{6}\right)=\frac{5}{72} \text { ) }\end{array}$