a)
100% impur - 10% impuritati = puritate 90%
100% ................... 120g sare impura
90% ...................... md = 108 g sare pura
m.apa= 400 g
ms= md+m.apa = 108+400 = 508g sol
c% = mdx100/ms = 108x100/508 = 21,26%
b)
600 g apa initiala - 100 g apa evaporata = 500g
md = 160 g sare
=> ms = md+m.apa.ramasa = 160+500 = 660 g sol
c% = mdx100/ms = 160x100/660 = 24,24%