Răspuns:
c2=26.(6)%
Explicație:
Inainte:
c1=12%,
masa de substanta (saramura): ms=100g.
Masa de sare md ce da concentratia c1:
c1=md×100/ms
12=md×100/100=md.
Acum se adauga inca 20g de sare.
md2=md+20=12+20=32g
Masa de substanta (saramura) devine:
ms2=ms+20=100+20=120g
Noua concentratie:
c2=md2×100/ms2=32×100/120
c2=3200/120=320/12=80/3=26.(6)%
