Răspuns :
Metoda I
1+2+3+...+98+99+100=
=(1+100)+(2+99)+(3+98)+.....+(50+51)=
=101+101+101+....+101(de 50 ori)=
=101x50=5050
Metoda II
Termenii sumei sunt in progresie aritmetica cu ratia 1.
S=(1+100)*100/2=10100/2=5050
1+2+3+...+98+99+100=
=(1+100)+(2+99)+(3+98)+.....+(50+51)=
=101+101+101+....+101(de 50 ori)=
=101x50=5050
Metoda II
Termenii sumei sunt in progresie aritmetica cu ratia 1.
S=(1+100)*100/2=10100/2=5050