Label the bags
There are three bags.The first bag has two blue rocks. The second bag has two red rocks. The third bag has a blue and a red rock. All bags are labeled but all labels are wrong.You are allowed to open one bag, pick one rock at random, see its color and put it back into the bag, without seeing the color of the other rock.
How many such operations are necessary to correctly label the bags ?
The answer is 1.
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1 solution
Open the bag labeled one blue one red. If one is red, the other is red too. If its blue, the other is blue as well. If its red, the bag labeled blue is the mixed bag and the third one is the one with 2 blue rocks.