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calculati :5+10+15+20+......+100


Răspuns :

5 + 10 + 15 + 20 + .... + 100 =
5(1 + 2 + 3 + 4 + ...... + 20) =
5 * 20 * (20 + 1) : 2 =
5 * 21 * 10 = 
1050 
5+10+15+20+25+30+35+40+45+50+55+60+65+70+75+80+85+90+95+100=1050