Question

Un elev are o suma de bani. In prima zi cheltuieste o jumatate din suma,a doua zii o treime din rest,a treia zii o jumatate din noul rest,iar a patra zi o treime din suma ramasa. Dupa aceste cheltuieli ii mai raman 80lei.

Answer 1

Răspuns:

x=suma initiala de bani

x/2 - prima zi

x-x/2=x/2 r₁

x/2·1/3=x/6 -a2a zi

x/2-x/6=x/3 r₂

x/3·1/3=x/6 - a3a zi

x/3-x/6=x/6 r³

x/6·1/3=x/18 - a4a zi

x/2+x/6+x/6+x/18+80=x

9x+3x+3x+x+1440=18x

1440=18x-16x

x=1440:2

x=720 suma initiala

V:720-720:2-720:6-720:6-720:18=720-360-120-120-40=80 lei ramasi