You have eight bags, each of them containing 48 coins.

Five of these bags contain only true coins, the rest of them contain fake coins. Fake coins weigh 1 gram less than the real coins.

You do not know what bags have fake coins and what bags have real coins. You do not know also, besides that it is an integer value, the weight of the real coins.

You can use a digital or analog reading scale with precision up to 1 gram.

Making only one weighing and using the minimum number of coins, how can you find the bags containing the fake coins?

(In reply to Looking for an answer by Leming)

Leming:

You can convert your solution into Charlie's better solution by taking one less coin from each bag.  No matter which bag has the fakes, taking one less coin from each reduces the total weight by 5 true coins and 3 fake coins, so Charlie's solution works the same way that yours does, with 8 fewer coins.

Posted by Steve Herman on 2008-10-23 23:32:06