Răspuns :
11(1 + 2 +3 +..........+100) = 11·100·101:2 = 11·50·101 = 55550
Scriem operatia asa cum este:[tex]11+22+33+....+1100[/tex]
Dam factor comun pe 11 si avem [tex]11(1+2+3+...+100)[/tex]
Aplicam Suma lui Gauss[n*(n+1)]/2:[tex]11[100*(100+1)]/2=\ \textgreater \ 11(100*101)/2=\ \textgreater \ 5050*11=\ \textgreater \ \\
S_n= 55550[/tex]