Question

Calculati uramatorele sume a) 1+2+3...+30 b)2+3+4+...+30 c) 9+10+11+...+30

Answer 1

Explicație pas cu pas:

a)30×31:2=31×30:2=31×15=465

b)2×(30×31:2)=2×(31×15)=2×465=930

c)3×(30×31:2)=3×(31×30:2)=3×(31×15)=3×465=1395