Question

Aflati
Cifra zecilor N=301+302+303+....+349

Answer 1

N=301+302+303+...+349

N=300+1+300+2+300+3+...+300+49

N=300•49+1+2+3+...+49

$n = 14700 + \frac{49 \times 50}{2}$

N=14700+49•25

N=14700+1225

N=15925 => cifra zecilor este 2