Question

O persoana avea o suma de bani pe care a cheltuit-o astfel:in prima zi 40% din suma,iar in a doua zi 60% din rest.Daca in a treia zi a cheltuit cu 72 lei mai putin decat in prima zi,aflati suma de bani cheltuita in cele trei zile.

Answer 1

Răspuns:

Explicație pas cu pas:

Notam cu x suma totala de bani

$Prima ^{ } zi \\\\40:100*x =\frac{2x}{5}$

restul după ce a cheltuit in prima zi

$x-\frac{2x}{5} = \frac{5x-2x}{5} = \frac{3x}{5}$

$II ^{ ^{} } zi\\ \\\frac{60}{100}*\frac{3x}{5} = \frac{3}{5} * \frac{3x}{5} =\frac{9x}{25}$

$III ^{} {} zi \\\\\frac{2x}{5}-72= \frac{2x-360}{5}$

adunam cat a cheltuit in fiecare zi

$\frac{2x}{5} +\frac{9x}{25} +\frac{2x-360}{5} = x \\ \\10x+9x+10x-1800=25x\\\\29x-1800=25x\\\\29x-25x=1800\\\\4x=1800\\\\x = 450 lei$

suma cheltuita in prima zi: $\frac{2*450}{5} = 180$ lei

suma cheltuita in a doua zi:  $\frac{9 * 450}{25} = \frac{4050}{25} = 162 lei$

suma cheltuita in a treia zi: 180 - 72 = 108 lei