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Cel mai inteligent răspuns!
2014-08-23T14:13:45+03:00
1) cp=md/ms *100

cp-concentratia procentuala
md-masa substantei dizolvate
ms-masa solutiei

ms=md + m H2O

3,6l= 3,6kg= 3600g

cp= 400/(400+3600) *100

cp= 400/4000 *100

cp=400/40

cp=10%

2)-1 +2 -3 + 4-5+.....-199+200=

= -1 -1-1.....-1   } de 100 ori

= -1*100=  -100
aha
dupa -5 nu trebuia - inloc de +?
nu, vine +6 -7
aha ms
:)