ms1 = 360g , c1 = 23%
ms2 = 540g , c2 = 12%
---------------------------------/---
c%finala = ?
--------------------------------//--
c% = mdx100/ms
=> md1 = ms1xc1/100 = 360x23/100 = 82,8g
=> md2 = ms2xc2/100 = 540x12/100 = 64,8g
md.final = md1+md2 = 82,8+64,8 = 147,6g
ms.final = ms1+ms2 = 360+540 = 900g
=> c%final = md.finalx100/ms.final
= 147,6x100/900 = 16,4%