Express the following binary numbers into their equivalent octal numbers:

(a) 100101111

(b) 111011010

(c) 1010011

(d) 10011101

(a) 100101111

Grouping in bits of 3:

$\underlinesegment{100} \quad \underlinesegment{101} \quad \underlinesegment{111}$

Therefore, (100101111)₂ = (457)₈

(b) 111011010

Grouping in bits of 3:

$\underlinesegment{111} \quad \underlinesegment{011} \quad \underlinesegment{010}$

Therefore, (111011010)₂ = (732)₈

(c) 1010011

Grouping in bits of 3:

$\underlinesegment{001} \quad \underlinesegment{010} \quad \underlinesegment{011}$

Therefore, (1010011)₂ = (123)₈

(d) 10011101

Grouping in bits of 3:

$\underlinesegment{010} \quad \underlinesegment{011} \quad \underlinesegment{101}$

Therefore, (10011101)₂ = (235)₈