Question

O persoana are o S de bani .In prima zi cheltuieste 3 supra 10 din S , a doua zi 2 supra 5 din suma S ,iar a treia zi 25 % din S. Stiind ca persoanei îi ramane 600 de lei , determinati suma de bani cheltuita in prima zi.

Answer 1

S - (3/10 * S+2/5 * S+25/100 * S) = 600
S - (3/10 * S+2/5 * S+1/4 * S) = 600 aducem la acelasi numitor
S - S * (6/20 +8/20+5/20)=600
S-S*19/20=600
1/20 *S = 600
S = 12000 lei

Answer 2

I zi:
$\frac{3}{10} s$

II zi
$\frac{2}{5} s$

III zi
$\frac{25}{100} s = \frac{1}{4}s$

restul=600 lei

$s - ( \frac{3}{10} s + \frac{2}{5}s + \frac{1}{4} s) = 600$

$s - ( \frac{6s + 8s + 5s}{20}) = 600$

$s - \frac{19s}{20} = 600$
$20s - 19s = 12000$
$s = 12000 \: lei$

I zi

$\frac{3}{10} \times 12000 = 3600 \: lei$