Question

Un elev are o suma de bani. In prima zi cheltuie 1/3 din suma, a doua zi 20% din rest, a treia zi 1/3 din noul rest si ii mai raman 960 lei. Ce suma a avut elevul la inceput?

Answer 1

Prima zi: x-1/3*x=2/3*x
Adoua zi:
20/100*2/3*x=1/5*2x/3=2x/15
A treia zi:
x-(1/3x+20/100*2/3*x)=x- (x/3+2x/15)= x-7x/15=8x/15 (noul rest)
1/3*8x/15=8x/45
Rezolvare:

1/3*x+2x/15+8x/45+960=x
15x+6x+8x+960*45=45x
45x-29x=960*45
16x=960*45
x=960*45/16
x=2700 lei