How do you do the calculation for this to get the total weight of the mixture?

Question

Refer to
http://answers.yahoo.com/question/index;_ylt=As_fcJgK1bPe5.yNQwRiQ0bsy6IX?qid=20060629113439AAeFW99

Total mass I mean

When you don't know the total volume but you don't know the volume of the individual substances.

Correction: When you DO know the total volume.

Answer 1

Consider the following statement:
A syrup solution contains 40% by weight of syrup.

This means that in every 100 gm (or 100 kg or 100 lbs, whatever be the units) of the SOLUTION, there is 40 gm (or 40 kg or 40 lbs) of SYRUP. This also means that every 100 gm of solution contains (100 - 40 =) 60 gm of water.

ALERT: This statement doesn't mean that every 100 cc of the solution contains 40 cc of syrup and rest 60 cc of water BECAUSE cc or cubic centimetre is the unit of volume; not a unit of mass. The statement would have meant this had the term be "% by volume" and not "% by mass" or "% by weight".

Thus, by the term "% by mass" or "% by weight" it means how much mass of a ingradient is present in 100 units of mass of the mixture.

Answer 2

It means that if you take all the weight of B and add A to it, at the end, the total mass of A will be 3% of the total mass of A+B

If you know the volume, you need densities to calculate mass.