ms1 = 500 g , c1 = 20% , c%= mdx100/ms
md = ms1xc1/100 = 500x20/100 = 100 g
notam cu X masa de apa ce trebuie adaugata..... (si NU evaporata.... vorbim de scaderea concentratie unei solutii prin diluare adica adaugare de apa
ms2 = ms1 + X
=> ms2 = mdx100/c2
=> ms1+X = mdx100/c2 <=> (500+X)5 = 100x100
=> 500+X = 2000 => X = 2000-500 = 1500 g apa