ms1 = 500 g
c1% = 20%
m= 50 g
-----------------------------/-------
c2% = ?%
-----------------------------//------
stim ca c% = mdx100/ms
md1 = ms1xc1/100 = 500x20/100 = 100 g
=> md2 = md1 + m = 100 + 50 = 150 g
=> ms2 = ms1 + m = 500 + 50 = 550 g
=> c2% = md2x100/ms2 = 150x100/550 = 27,27%