ms1= 50 g
c1= 20%
ms2= 100 g
c2= 50%
---------------------/---
c.f. = ?%
---------------------//---
ms.f = ms1+ms2 = 50+100 = 150 g
c% = mdx100/ms
=> md1= ms1xc1/100 = 50x20/100 = 10 g
=> md2= ms2xc2/100 = 100x50/100 = 50 g
=> md.f = md1 + md2 = 10+50 = 60 g
c.f. = md.fx100/ms.f = 60x100/150 = 40%