Example 12 Convert $(111001101010)_2$ to an octal number.

Translate the above text into English, keeping the original text's line breaks and format, and output the translation result directly.
The first step is to divide this binary number into groups of three digits: $(111001101010)_{2}=\left(\begin{array}{llll}111 & 001 & 101 & 010\end{array}\right)_{2}$. Then, use the formula in (2.2):

$$\begin{array}{ll}
(111)_{2}=(7)_{8}, & (001)_{2}=(1)_{8} \\
(101)_{2}=(5)_{8}, & (010)_{2}=(2)_{8}
\end{array}$$

Thus, we get
$$(111001101010)_{2}=(7152)_{8}$$