Question:

A one-armed surgeon needs to operate on three patients, one after another. But the surgeon has only two individual surgical gloves. How can the surgeon operate on the three patients in turn without risking infection for the patients or for himself?

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Solution: Safety in this case necessitates that every operation requires a surgical glove whose surface has not been contaminated. This is for the protection of the patients as well as the surgeon. The interviewer is looking for you to find the “aha!” factor that will allow an elegant solution to this puzzle. Please don’t even bother to think about creative ways to reuse surgical gloves.

To start, it’s always good for the candidate to repeat the puzzle:

Let me see if I have this. The situation is that the one-armed surgeon needs three clean gloves for three patients but has only two gloves. In other words, how can the surgeon operate safely with three patients using just two gloves? The gloves not only protect the patients from the surgeon, but ensure that no diseases are passed from one patient to the other.

I’m aware of only one satisfactory answer:

The solution starts with the surgeon putting on two gloves, one over the other. She then operates on patient number 1. Then the surgeon removes the outermost glove, leaving the other one on. She now operates on patient number 2. Finally the surgeon takes the glove discarded from the surgery with patient number 1, reverses it, and puts it on over the remaining glove. She can then operate on patient number 3.

The puzzle is actually more compelling in its original wording, involving a man with two condoms and three partners. It has been reworded here to work, more or less, in the present context. Don’t even ask how a one-armed surgeon changes gloves.

Answer: Put on two gloves, one over the other, and then reverse the first glove.