Question

rezultatul calcului 5 +10+15+.....+40 este egal urgent

Answer 1

5+10+15+...+40=
5(1+2+3+...+8)=
5*[8*(8+1):2]=
5*[(8*9):2]=
5*(72:2)=
5*36=
180

Answer 2

$\displaystyle 5+10+15+...+40=5(1+2+3+...+8)=5 \times \frac{8(8+1)}{2} = \\ \\ =5 \times \frac{8 \times 9}{2} =5 \times \frac{72}{2} =5 \times 36=180$