The solution to yesterday’s puzzle was deduced by some in the comments. I was not able to solve the puzzle myself but in such cases, once I know the solution, I try to figure out why I could not figure it out, to see what I had overlooked.
In this case there are four possibilities for the two coin tosses: HH, HT, TH, and TT where H stands for heads and T for tails. The two coin tosses are independent of each other and so knowing the result of one doesn’t enable one to predict the result of the other. This tempted me to ignore (or not properly register) the information that each person gets to see the result of his or her own toss before predicting the other. And since the captives each gets to make just one guess, that seemed to me to suggest that they must guess wrong at some point.
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