chemistry
posted by Hank .
a hydrated salt is a solid that includes water molecules within its crystal structure. a student heated a 9.10gram sample of a hydrated salt to a constant mass of 5.41 grams. what percent by mass of water did the salt contain?

mass water = 9.105.41 = ??
%H2O = (mass H2O/mass sample)*100 = ? 
is the answer 40.5% or 59.5% ?

You can't possibly follow my instructions and come up with two possible answers.

well i got 3.69% but that doesnt look right

Frankly, I don't think you can get that, either, at least not legally.
mass water = 9.105.41 = 3.69 g H2O. I don't know how you converted that into percent; however, take the 3.69 g, substitute into the percent formula I gave you and solve for % H2O.
Post your work if you get stuck. 
9.105.41=3.69
18.0152/3.69=?? 
Look. Just follow the instructions. You posted a question, I gave you the answer, now you're making up your own answer. I have copied my instructions below. Follow them.
mass water = 9.105.41 = ??. Then
%H2O = (mass H2O/mass sample)*100 = ?