Răspuns:
c=mdx100/ms, unde ms= md+m,apa
ms1= 300g c1=20%---> md1= c1xms1/100= 20x300/100g= 60g
in solutia a doua/
md2= md1+10=>70g
ms2=ms1+md+m,apa= 300+10+20=> 320g
c2= 70x100/320=21,9%
prin impartirea solutiei in vase diferite, nu se modifica conc.
Explicație: