Question

2)Calculeaza suma numerelor de trei cifre scrise cu cifre identice.Grupeaza convenabil termenii pt a calcula rapid.
Ajutatti-ma si la acesta va rog.

Answer 1

111+222+...+999=
=(111+999)+(222+888)+(333+777)+(444+666)+555=
=1110+111=+1110+1110+555=
=4*1110+555=
=4440+555=
=4995

Answer 2

111+222+333+444+555+666+777+888+999=999+111+888+222+777+333+666+444+555=1110+1110+1110+1110+555
=4995