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ce cantitate de zahar trebuie sa adaugam in 300 g solutie 2%pt a obtine o solutie de 40%

Răspuns :

C=md/ms*100=>md=C*ms/100=2*300/100=6g 

ms=md+mH2O=>mH2O=ms-md=300-6=294g

C=md/md+mH2O*100 ;  40=md/md+294*100 => 40md+11760=100md => 60md=11760=>md=196g

md adaugat = 196-6=190g zahar