My friend Jean told me this interesting puzzle:
Four teenagers, two male and two female, are in a hotel room. They want to have heterosexual sex in all possible combinations, so that each guy has sex with each girl. However, they have only two condoms. How can they fulfill their sexual fantasies while still practicing safe sex?
This situation is kind of ridiculous. I mean, where are they that they can’t just get more condoms? And why can’t they just be happy having sex with just one other person? But still, if they’re teenagers (which wasn’t in the original problem I think, but I just assumed), I suppose it’s plausible that they’re just that horny. And maybe all the convenience stores are closed.
I’ll put the answer at the end of this post. But I think the interesting part about this puzzle is not the answer to it, but the question of how to state the same puzzle, but in a G-rated way. Because you’d think that this kind of situation could come up, just without involving genitals and possible STDs.
But I think it’s surprisingly hard to come up with a “clean” version of the problem, because sex is just special like that. You could imagine some contrived scenarios involving people with rubber gloves reaching into petri dishes with bacteria or something of that nature, but these situations quickly become very unbelievable (even more so that the original) because it’s hard to imagine a situation where two different people would have to put their gloved hand/foot/tongue into the same place, other than for the purposes of having an orgasm inside a different person.
I think there has to be some kind of biological component analogous to the semen and vaginal fluid of the original. Otherwise, there’s no danger of infection or contamination, which is really central to the puzzle. But why would two different people have to each expose themselves to two different contaminants? Oh but maybe if they’re surgeons. Each with a different specialty. So here’s my attempt, which I’ll call “Two Surgeons Trying to Save the World’s Latex Production”:
Two critically injured latex technicians, both with critical injuries to their heart and brain, are the only two people left who can operate the world’s last latex processing plant. They’re brought to a hospital where the world’s best cardiologist and the world’s best neurosurgeon are on the staff, and each doctor is the only one who can save the patients’ hearts and brains, respectively. Unfortunately, due to the latex shortage, the hospital has only two sets of rubber gloves left. The two latex technicians unfortunately both have different blood-borne illnesses that are highly contagious. In addition, the doctors both have extremely sensitive hands, and if they use other people’s gloves, their hands become terribly swollen, leaving them unable to operate. How can the two doctors save both patients without exposing either of them to infections?
The latex shortage might also explain why the four teenagers only had two condoms available. OK, so this situation is highly contrived too, as well as sounding apocalyptic. And I almost said that the two latex technicians were extremely promiscuous and had HIV, but then I remembered that this was supposed to be a sex-free version. It just goes to show you, it’s really hard to come up with a situation analogous to the condom situation without actually involving condoms and sex.
Oh so the answer to the original problem. Let’s call the guys Andrew and Brian, and the girls Cindy and Debby, just so we don’t have to refer to them as “Person A” and so forth. Andrew first puts on condom 1 and then condom 2 on top of that, and he has sex with Cindy. He then removes condom 2, leaving condom 1 on, and has sex with Debby. Now Brian puts on condom 2, which is clean on the inside but has Cindy’s vaginal fluids on the outside, and has sex with Cindy. He then puts on condom 1, which has Andrew’s semen on the inside and Debby’s vaginal fluid on the outside, on top of condom 2, and has sex with Debby. Mission complete.
But now the question remains: if they’re all so concerned about having safe sex, why are they engaging in a dangerous practice like double bagging?