Metoda I: metoda grafica
aplicam regula dreptunghiului
c1= 8% --------------------> 20-17 = 3 parti masa sol. 8%
c.f.= 17%
c2= 20% -----------------> 17-8 = 9 parti masa sol. 20%
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total parti masa sol. 17% = 3+9 = 12
=>
12 parti sol. 17% .......... 3 parti sol. 8% .......... 9 parti sol. 20%
ms.final ........................... ms1 .......................... ms2
=> ms1/ms2 = 3/9 = 1/3
ms1: ms2 = 1 : 3
Metoda 2: metoda algebrica
ms1 = ?g, c1= 8%
ms2 = ?g, c2= 20%
c.f.= 17%
stim ca c% = mdx100/ms
=> c1 = md1x100/ms1 <=> ms1 = 12,5md1
=> c2 = md2x100/ms2 <=> ms2 = 5md2
=> sol.finala este formata din md.final si ms.final
=> md.final = md2 + md1
=> ms.final = ms1 + ms2 = 12,5md1 + 5md2
=> c.f. = md.finalx100/ms.final
=> 17 = (md1+md2)100/12,5md1 + 5md2
=> 212,5md1 + 85md2 = 100md1 + 100md2
=> 112,5md1 = 15md2 => 7,5md1 = md2
=> ms1 = 12,5md1 si ms2 = 5md2 = 37,5md1
=> ms1: ms2 = 12,5md1 : 37,5md1 /:12,5md1 = 1 : 3
