THE TEN COIN BAGS
On the table in front of you you can see ten bags filled with ten
coins each, but the coins in one of the bags are all fakes. The only
thing known about a fake coin is the fact that its weight differs by
exactly one gram from the weight of a valid coin (which is an integer
number greater than 0), but not whether it is heavier or not. You are
allowed to use a one-plate scale which gives the weight in grams. If
you're only allowed to use this scale ONCE, how would you try to find
the bag with the fake coins?