Question

5+10+15+......+125




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Answer 1

S=5+10+15+......+125=5(1+2+3+...+25);

Formulă: 1+2+3+...+n=n(n+1)/2;

=>S=(5×25×26)/2=1625;

Answer 2

Răspuns:

1x5+2x5+3x5+.....5x25

5x(1+2+3+....25)

5x25x26:2

125x13

1625