Question

1. Calculati:

a) 1+2+3+...+88= ?

b) 2+4+6+...100= ?

AJUTATI-MA VA ROG FRUMOS !!!

Answer 1

Suma lui Gauss la ambele
a).
S=[(1+88)*88]/2=89*88/2=3916

b).
Dai factor comun 2 si ai
S=2(1+2+3+.........+50)=2*[(1+50)*50]/2=(2*51*50)/2=2550

Answer 2

$\displaystyle a).1+2+3+...+88= \frac{88(88+1)}{2} = \frac{88 \times 89}{2} = \frac{7832}{2} =3916 \\ \\ b).2+4+6+...+100=2(1+2+3+...+50)=2 \times \frac{50(50+1)}{2} = \\ \\ =2 \times \frac{50 \times 51}{2} =\not 2 \times \frac{2550}{\not 2} =2550$