Seperating Mixtures, changes in Weight

[oray]

Homework Statement

You start with 10.00 g of sand/salt mixture. suppose you end up with 4.52g of sand and 5.9g of salt.

a) calculate the % sand and salt based only on the sand result: "4.52 g sand means there must have been 5.48g of salt"

b) do the same using only the salt result: "5.9g salt means there must be 4.1g of sand"

c) suggest some likely reasons why your total is not the 10.00g you started with

Homework Equations

I've figured out part a) and b) with relative ease, but i don't even know where to begin with part c.

The Attempt at a Solution

one reason could just be human error in measurements, but i don't think that's what my teachers looking for. That is as far as I've gotten.
Perhaps there is some reason why the overall weight of two substances would increase after they are separated?

 

[Fightfish]

You may want to think along the lines of the separating process i.e. how are they separated.