You can calculate the density (mass per unit volume) easily enough:

42kg/7l = 6kg/l



Now you can use the density to compute volume of a given mass, by dividing:

  V = 63kg / (6kg/l) =  10.5l 





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For this problem,  a proportion would also work:



  7/42 = x/63  -->  x = 63*7/42 = 10.5 

Answer by josgarithmetic(39617)   (Show Source): You can put this solution on YOUR website!
 Density is being taken as a constant. 

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