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11+22+33+.......+7700=? Dau coroana.

Răspuns :

=11×1+11×2+11×3+...+11×700=

=11(1+2+3+...+700)=

[tex]=11*\frac{700*701}{2}=[/tex]

=11×350×701=

=3.850×701=

=2.698.850