That doesn't work exactly.
Because you must find out if it's heavier or lighter. And
you'll need the second measurement to find out if the cube is in it, although if it is lighter, then of course it's easy to find out with the third measurement. But if you chose the "wrong" group, you'll know the cube is heavier, but have only one measurement left to find out which one of four it is. Impossible. In case 3 things look good from there on, but not using the method you described. Because you don't even know if the cube would be heavier or not.
Failed! Try again! Or i'll have to assume you're brainless.
Fealiks: another post like that and i'll have to do .. nothing. I have no moderator powers. Sadly enough. But be informed, this thread is for using your brain, only
. And for making clear that i usually don't look like a dumbnut. On the other hand.. you have only 3
tries, not 11