Question

vreau si eu 3 exercitii cu suma gauss de clasa a 5-a

Answer 1

1+2+3+.........+25=25(25+1):2=25x26:2=325
2+4+6+8+.........+62=2(1+2+3+4+......+31)=2x31x(31+1):2=2x31x32:2=992

3+6+9+............+27=3(1+2+3+......+9)=3x9x(9+1):2=3x9x10:2=135