Calculeaza 11+22+55+...+99 DAY COROANA CINE RASPUNDE PRIMUL

Răspuns :

11+22+33+........+99=11·(1+2+3+4+5+6+7+8+9)=11·45=495
11+22+55+...+99=

=11(1+2+...+9)

=11
·9·10:2


=11·9·5

=495