ms1 = 400g NaCl
C1 = 10%
ms2 = 200g NaCl
C = 30%
C1 = md1/ms1*100 => md1 = C1*ms1/100 = 10*400/100 = 40g NaCl
C2 = md2/ms2*100 => md2 = C2*ms2/100 = 30*200/100 = 60g NaCl
a. md final = 40+60 = 100g NaCl
b. ms1 = md1+mH2O => mH2O = ms1-md1 = 400-40 = 360g
ms2 = md2+mH2O => mH2O = ms2-md2 = 200-60 = 140g
mH2O totala = 360+140 = 500g
m H2O : md final = 500:100 = 5:1