Question

O persoana cheltuieste o suma de bani in 3 zile astfel : in prima zi 2/3 din suma si inca 15 lei, a doua zi 2/5 din rest, iar a treia zi restul de 27 de lei.
Aflati suma initiala.

Answer 1

fie x suma initiala, vom scrie in functie de x cat a cheltuit zilnic:

I) 2/3x+15

II) 2/5[x-(2/3x+15)]=...=2/15x-6

III) restul de 27 lei

Putem scrie ecuatia:

x-(2/3x+15)-(2/15x-6)=27 => x-2/3x-2/15x -15+6=27=>....

3/15x=36 => x=36x15/3=180 lei