you have ten bags each bag has coins in it ( doesnt matter how much) each coin weighs 10 grams exept for one bag that has fake coins and each coin weighs less than ten grams ( doesnt matter how less, 9 grams 8 grams) just by holding the coins in your hand you cant tell which bag is the one with fake coins and you have a scale. with one weighing you need to find out which bag is fake...

The weigth of the fake coins DOES matter, if all fake coins would weigh 1 gram you could defenitely determine the fake bag by weighing the bags in your hands.

Originally posted by TheMaster37 The weigth of the fake coins DOES matter, if all fake coins would weigh 1 gram you could defenitely determine the fake bag by weighing the bags in your hands.

its a riddle not a real life situationπππ
the point is that you need to weigh the coins on the scale and you CANT weigh them with your hand or else whats the oint of the riddleππ

Hmm...taking coins out of the bag...what if you take one coin from the first bag, two coins from the second...etc...until you get 55 coins in total (from ten bags), then weigh it.

You should end up with 550g but you won't. I'm still trying to think how you figure out which bag is the odd one out...

Do you know how much the fake coins weigh, because if you do, I think I can work it out by working out the difference and finding out which bag has the fake coins...

now let's make this one a little bit more difficult:

Suppose all fake coins weigh 9 grams. Yous still got 10 bags of coins but you might have more than just one bag with fake coins, but you don't know how many bags are fake and how many not. How can you determine with only one weighing HOW MANY and WHICH of your 10 bags has fake coins in it?

Originally posted by Kandinsky now let's make this one a little bit more difficult:

Suppose all fake coins weigh 9 grams. Yous still got 10 bags of coins but you might have more than just one bag with fake coins, but you don't know how many bags are fake and how many not. How can you determine with only one weighing HOW MANY and WHICH of your 10 bags has fake coins in it?

Okay, this is a new one for me, but I did find the solution. Again, I'll send my solution to the poster to not spoil it for others.

Hint: My solution requires a large number of coins in the bags of coins due to the fact that there are 10 bags of coins.
There is a further one-word hint that should help most folks solve this one. π

Originally posted by Kandinsky now let's make this one a little bit more difficult:

Suppose all fake coins weigh 9 grams. Yous still got 10 bags of coins but you might have more than just one bag with fake coins, but you don't know how many bags are fake and how m ...[text shortened]... weighing HOW MANY and WHICH of your 10 bags has fake coins in it?

Can we assume each bag has as many coins as we like? If so, do the following: put 1 coin from bag 1, 2 from bag 2, 4 from bag 3, 8 from bag 4 etc. on the scales. Suppose these weigh n grams; then work out 10230 - n, and put it in binary. Each '1' indicates a bag of fake coins, with the first bag on the right and the last on the left.

Think I have guessed it? You get on the cales with all bags, drop (dispose of a bag) and if the scale drops by an amount less than (is it 10 grams sorry forgot what the weight was) the weight of the real coins then the last bag dropped is the bag with fake coins. Is that the correct answer?
Steve