Question

Determinați suma a 5 + 6 + 7 +... +56​

Answer 1

 

$\displaystyle\bf\\5+6+7+...+56=?\\\\\textbf{Calculam numarul de termeni (n).}\\\\n=56-5+1=51+1=52~de~termeni.\\\\Folosim~formula~lui~Gauss:\\\\5+6+7+...+56=\frac{n(56+5)}{2}=\frac{52\times61}{2}=26\times61=\boxed{\bf1586}$