There are 4 identical tumblers each filled with the same number of 1 kg balls. One of these four tumblers contains all defective underweight balls. You have a weighing scale which you can use to weigh the tumblers, but it can be used only once.
How can you figure out which tumbler contains the defective balls?
Note: The tumblers are not transparent, but it doesn't matter, because the underweight balls look and feel the same as the genuine balls anyway. Underweight ball can be between (0,1).
I am not the original author of this question. This question was asked in an interview to my friend and he agrees that this is not solvable until and unless there are restrictions put on the underweight quantity. I don't wish to modify the question now and have accepted the answer which concurs with this.