Question

Calculați 19+20+21+22+...+39​

Answer 1

Răspuns:

19+20+21+22+...+39=

39×(39+1):2=

39×40:2=

1.560:2=

=780

Answer 2

Aplicam formula pentru sume gauss :

$\frac{n(n + 1}{2}$

$\frac{39(39 + 1)}{2}$

$\frac{39 \times 40}{2}$

=780.