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calculati 111+222+333+...+999​

Răspuns :

111+222+333+...+999

=111×1+111×2+111×3+...+111×9

=111×(1+2+3+...+9)

=1+2+3+...+9=

=(9×10):2

=45

=>111+222+333+...+999=111×45=4995