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You have ten stacks of identical looking gold coins.
Nine of the stacks contain all real gold coins, and one of the stacks is made up entirely of fake gold coins. Each real gold coin weighs exactly 1 gram, while each fake gold coin weighs exactly 1.1 grams. Using a scale, how can you determine the stack of fake coins?
RULES: You can use to take only one measurement. For example, you stack what you want on the scale, press a button, and get a readout of the weight. You can do this only once, and once the readout is displayed it does not change if you remove any coins. You can mix the coins up in their stacks, separate them, mark them, whatever. How do you find out for sure which stack contains the fake gold coins?
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Take 1 from the first pile, 2 from the second 3 from the 3rd and so on. weigh all those coins together and you will get 55 whole grams and x*0.1 grams left over. the fake coins are in the xth pile.
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This question Was already brought up in The Maths Forum. I think sam,guv and Honeybee answered them too..
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Active I am just posting them for people in here to stop thinking for a second about what the are doing and take a break. When your mind goes away from anything that you are trying to solve. It's seems to be easier to solve. At least that is the case with me. It's just in the name of fun.
