x-cantitatea initiala de marfa
I zi: x-4x/9=(9x-4x)/9=5x/9
II zi: 5x/9-2/5·5x/9=5x/9-2x/9=3x/9=x/3
III zi: x/3-1/4·x/3=x/3-x/12=(4x-x)/12=3x/12=x/4
x/4=1125
x=4·1125
x=4500
verificare
I zi :4500·4/9= 2000 kg s-au scos
IIzi: 4500-2000=2500
2500·2/5=1000 kg s-au scos
III zi:2500-1000=1500
1500·1/4=375 kg s-au scos
1500-375=1125