Calculati:5+6+7+8+9+...+99

Răspuns :

Obs. Folosim formula sumei lui Gauss

1+2+..+n = n(n + 1) : 2

S = 5 + 6 + ... + 99 + 1 + 2 + 3 + 4 - 1 - 2 - 3 - 4

S = 99 x 100 : 2 - 10

S = 4950 - 10

S = 4940