200g Cu = 25%pur
masa pur = 25/100x250 = 62.5 g Cu
masa impuritati = 200-62.5 = 137.5 g
500g Zn = 90%pur
masa pur = 90/100x500 = 0.9x500= 9x50 = 450 g Zn
masa impur = 500g -450g = 50 g impur
Masa totala puritati = 137.5+450 = 587.5g
Masa totala impuritati= 50 + 137.5 = 187.5 g