Răspuns :
ms1 = 100 g, c1% = 20%
ms2 = ? g , c2% = 50%
ms.final = ? g c%final = 25%
aplicam regula dreptunghiului
c1= 20% ---------------------> 50-25= 25 parti masa sol. 20%
c.final= 25%
c2= 50% --------------------> 25-20= 5 parti masa sol. 50%
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total = 25+5 = 30 parti masa sol 25%
30 parti sol. 25% .............. 25 parti sol. 20% ........ 5 parti sol. 50%
ms.final ............................. ms1 = 100 g.............................. ms2
=> m.final = 30x100/25 = 120 g
=> ms2 = 100x5/25 = 20 g sol. 50%
r = ms1/ms2 = 25/5 = 5/1