c% = md x 100 / ms
ms1 = 1 kg
c1% = 10% => md1 = ms1 x c1 / 100 = 10 x 1 / 100 = 0,1 kg
ms2 = 1 kg
c2% = 3% => md2 = ms2 x c2 / 100 = 3 x 1 / 100 = 0,03 kg
=> md tot. = md1 + md2 = 0,13 kg,
ms tot. = ms1 + ms2 = 2 kg,
c% final = md.tot x 100 / ms.tot => c% = 0,13 x 100 / 2 = 6,5%