Răspuns :
Notam S suma initiala
I) in prima zi cheltuie S/5
Mai are S-S/5 lei = 4S/5
II) 1/4 × 4S/5= S/5
Mai are 4S/5-S/5=3S/5 lei
III) 1/3 × 3S/5=S/5
Mai are 3S/5-S/5=2S/5
IV) 1/2 × 2S/5=S/5
Mai are 2S/5-S/5=S/5 lei
Dar ni se da ca mar are 5 lei
=> S/5=5 atunci S=25 de lei