do iron fillings or sea water weigh more?!
Answers:
with only that information, there is no answer. You have to have a method of comparing them... like say volume. 1 cubic foot of one versus 1 cubic foot of the other... and then compare. They have the same volume now, but the iron may indeed weigh more.
Or you can do it the other way... 1 pound of each. Of course they then weigh the same, but the volume will be different.
It's one of those questions teachers ask when they're bored and need to take a break while you worry over something so silly.