Question

1+2+3...+80
Cum se face ajutati-ma

Answer 1

(80*81):2
40*81
=3240

* = ori
Cu placere.

Answer 2

$\displaystyle 1+2+3+...+80= \frac{80(80+1)}{2} = \frac{80 \times 81}{2} = \frac{6480}{2} =3240$