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Calculeaza:5+10+15+...+300=?

Răspuns :

= 5(1 + 2 + ... + 60) = 5 × 60 × 61 ÷ 2 = 9150

5+10+15+...+300=
5(1+2+3+...+60)=
5 x (60x61)/2=
5x30x61=
150x61=
=9150
Succes!