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Care este suma ?

Posted: Fri Oct 24, 2008 6:31 pm
by miruna.lazar
Aflati suma : 5 + 10 + 15 ... + 355 .

Posted: Thu Nov 06, 2008 10:37 pm
by alex2008
\( 5+10+15+...+355=5(1+2+3+...+71)=5\cdot\frac{71\cdot72}{2}=12780 \)