5. Convert the following binary numbers to octal numbers:
(i) $(101101101)_{2}$,
(ii) $(101011001101001)_{2}$.
5 .
(i) Solution: The first step is to divide this binary number into groups of three digits, $(101101101)_{2}=\left(\begin{array}{ll}101 & 101101\end{array}\right)_{2}$, then use the formula in (2.2) $(101)_{2}=(5)_{8}$, which gives $(101101101)_{2}=(555)_{8}$.
(ii) Solution: The first step is to divide this binary number into groups of three digits, $(101011001101001)_{2}=(101011001101001)_{2}$, then use the formula in (2.2) $(101)_{2}=(5)_{8},(011)_{2}=(3)_{8},(001)_{2}=(1)_{8}$, which gives
$$(101011001101001)_{2}=(53151)_{8}$$