Question

Calculati:3+6+9+12+......+2019;

Answer 1

S=3+6+9+..+2019
S=3(1+2+3+..+673)  Aplicăm suma lui Gauss
S=3 × $\frac{673*674}{2}$
S= 3 ×$\frac{453602}{2}$
S=3×226801
S=680403
Baftă!

Answer 2

3 + 6 + 9 + 12 + .........+ 2019 = 
3(1 + 2 + 3 + 4 + ......  + 673) = 
3 * 673 * 674/2 =
3 * 673 * 337 = 
680 403