I read this interesting puzzle the other day... and thought I'd share it with you to boggle your minds...! I'd love to hear your thoughts!
For unknown reasons, a woman is told that she needs to take a drug which will wipe her memory and put her to sleep.
The doctor says that he will toss a coin. If it lands heads, he will administer the drug and a few minutes later she will wake up with no memory of the past. If it lands tails, he will do exactly the same, but then administer the drug one more time so she falls asleep for a second time, again waking with no memory of the past.
The woman wakes up and the doctor asks, "What are the chances that the coin landed heads?"