calculati 3+6+9+...+30

Răspuns :

= 3(1 + 2 + .. + 10)


= 3×10×11÷2


= 165

Aplicam suma lui Gauss
3+6+9+...+30
3*(1+2+3+.....+10)
3*10*(10+1):2
3*10*11:2
3*5*11
15*11
165