Ta có: \(\overline{abcdeg}\) = 10000.\(\overline{ab}\) + 100.\(\overline{cd}\) + \(\overline{eg}\)
= (9999.\(\overline{ab}\) + 99.\(\overline{cd}\) ) + ( \(\overline{ab}\) + \(\overline{cd}\) + \(\overline{eg}\))
Theo bài ra, ta có: \(\overline{ab}\) + \(\overline{cd}\) + \(\overline{eg}\) \(⋮\) 11
Vì 9999.\(\overline{ab}\) + 99.\(\overline{cd}\) \(⋮\) 11 và \(\overline{ab}\) + \(\overline{cd}\) + \(\overline{eg}\) \(⋮\) 11
nên (9999.\(\overline{ab}\) + 99.\(\overline{cd}\) ) + ( \(\overline{ab}\) + \(\overline{cd}\) + \(\overline{eg}\)) \(⋮\) 11
Vậy \(\overline{abcdeg}\) \(⋮\) 11