ms1 = 400g, c1% = 50%
c2% = 80%
c% = mdx100/ms => md = ms1xc1/100
= 400x50/100 = 200g
notam cu a = masa de apa evaporata
=> ms2 = ms1-a = 400-a
=> c2% = mdx100/ms2
=> 80 = 200x100/(400-a)
=> a = 12000/80 = 150g apa evaporata
facem proba:
ms2 = 400-150 = 250 g
c2% = 200x100/250 = 80%, deci verifica calculele de mai sus