Răspuns:
md=120g
mh2o=160g
ms=md+mh2o=120+160=280g
c=md×100/ms=120×100/280=42.85%
dublam concentatia=> c1=85.7
notam cu a cantitatea de zahăr care trebuie adaugata in aceeasi cantitate de apă.
c1=a×100/160+a
85.7=a×100/160+a
100a=85.7(160+a)
100a=13712+85.7a
14.3a=13712
a=958.88g zahăr