abc \(\div\)27 => a.100 + b.10 + c \(\div\) 27
=> 10. (a.100 + b.10 +c) \(\div\) 27
=> 1000a + 100b + 10c \(\div\) 27
(100b + 10c + a) + 999a \(\div\) 27
bca + 999a \(\div\) 27
Vì 999a \(\div\) 27 nên bca \(\div\) 27
Vậy: abc \(\div\) thì bca \(\div\) 27
< Chú ý: \(\div\) : chia hết >