Dawn Treader readers did well on this one. Stephen was the official winner. He broke the tape with the correct answer at 2:00 pm.
It only takes one coin to solve the problem.
We know that the jar labeled "MIXED" is not the mixed jar. It has to be one of only-the-same-year jars. So pull a penny from it and look at the year. Replace the MIXED label with the correct label (1975 if it was a 1975 penny etc). This will leave two jars that need to be corrected. One without a label and one with a label. We know the original labels were wrong. So take the label off of the labeled jar and move it to the unlabeled jar. Now put the MIXED label on the remaining jar.
Jim came up with the most original answer. Not sure it is correct, but it is original :-)
Of course it's correct! :)
Really, though, I believe there is a 0.5g loss of mass in pennies from 1975 to 2005.
Posted by: Jim A. | September 21, 2007 at 10:07
I instantly thought of the weighing option as well.
Couldn't it be argued that just because the labels are mixed up that one of them could still be labeled correctly? I mean if it is random then that should be a possibility and then the riddle is unsolvable except through weighing the jars. ;)
Posted by: Matt | September 25, 2007 at 08:50
Matt - that would be the case, except that "you know that the labels have been switched, so that each container is marked incorrectly"
Posted by: Paul | September 25, 2007 at 17:40