Question

Vlad cheltuieste 25% dintr-o suma de bani,apoi trei cincimi din rest,ramanandui 240lei .Ce suma a avut initial Vlad?

Answer 1

Notam cu S suma de bani initiala pe care a avut-o Vlad, iar r restul.
Calculam 25/100 * S + 3/5 * r = 240 <=> S/4 + 3r/5 = 240
 

Answer 2

Notam x suma de bani initiala!

$\frac{100x}{100}$-$\frac{25x}{100}$  =  $\frac{75x}{100}$ suma ramasa

$\frac{75x}{100}$*$\frac{3}{5}$ = $\frac{225}{500}$ = $\frac{45x}{100}$ a cheltuit a doua oara

$\frac{75x}{100}$-$\frac{45x}{100}$ = $\frac{30x}{100}$ = 240 lei <=> 30x=24000 <=> x = 800 lei

Vlad a avut initial 800 lei...