This is a good riddle I was asked today. There are 10 machines that make gold coins that weigh 10 grams, due to malfunction one machine makes coins that weigh 9 grams. You can only use a scale once. How do you determine what machine is not working? Please don't Google the answer. If you do take a guess please use the Spoiler tags to not ruin the fun. :icon_bigg [spoiler ]This is hidden from view until you hit the spoiler button.[/spoiler ] (without the spaces in the tags, of course) ^ if someone was unsure how to use them.
Spoiler You take 1 coin of machine number 1, 2 coins of machine 2, 3 coins of machine 3, and so on. Then you put all 55 coins on the scale together and from the number of grams missing on 550 you get the number of the machine (549 g would mean machine 1, 548 g machine 2 ...)
Spoiler I would take one coin from each machine and label them, coin one from machine one etc. Then, I'd put the coins on the scale, one by one, until the total weight is displaced by 9. (not removing any coins from the machine)
Not quite, your on the right path but I think that would count as more than one weighing. Because you would be getting more than one measurements of a weight. ---------- Post added 26th Feb 2013 at 12:51 AM ---------- That is correct.
