Question

Mihaela are o suma de bani. In prima zi ea cheltuieste 1/3 din suma , a doua zi 1/3 din rest , a treia zi 1/3 din noul rest , iar a patra zi restul, adica 16 lei. Ce suma a avut Mihaela ?

Answer 1

x=suma bani
x/3=ziua 1
x-x/3=2x/3 =rest
2x/3 * 1/3 =2x/9 =ziua 2
2x/3-2x/9=(6x-2x)/9=4x/9 =rest
4x/9 *1/3 =4x/27 =ziua 3
x/3+2x/9+4x/27+16=x
9x+6x+4x+432=27x
8x=432
x=54 lei

Answer 2

x-suma de bani ai Mhaelei
I zi:      x-x/3=(3x-x)/3=2x/3
II zi:    2x/3-1/3(2x/3)=2x/3-2x/9=(6x-2x)/9=4x/9
III zi:   4x/9-1/3(4x/9)=4x/9-4x/27=(12x-4x)/27=8x/27
8x/27=16
8x=16·27
x=432/8
x=54 lei suma avuta de Mihaela

I zi a cheltuit: 54x1/3=18 lei
II zi:        (54-18)x1/3=12 lei
III zi        (54-18-12)x1/3=8 lei
IV zi ::         16 lei
18+12+8+16=54