concentratia= (masa subst. dizolvate/ masa solutiei )·100
masa solutiei = masa apei + masa subst. dizolvate
ms=md+m apa
ms=1,5kg=1500g
c=24%
c=[md/(ms)]·100
md=c·ms/100
md=24·1500/100
md=360g=0,36kg
m apa=ms-md
m apa=1500-360
m apa=1140g=1,14kg
R: apa=1,14kg; sare=0,36kg