Question

cati termeni are suma 1+2+3+4+5+...,daca valoarea ei este un nr. format din doua cifre identice?

Answer 1

Sunt 2 cazuri:
1.
S =1+2+3+4+5.........+10
are 10 termeni
Suma Gauss cu formula de calcul : S= n(n+1):2=
 S= n(n+1):2=[10(10+1)]:2=(10×11):2=110:2=55
S =1+2+3+4+5.........+10 = 55
sau
2.
S =1+2+3+4+5.........+11
are 11 termeni
S= n(n+1):2=[11(11+1)]:2=(12×11):2=132:2 = 66
S =1+2+3+4+5.........+11 = 66

Answer 2

Am atasat rezolvarea!