When visiting a friend in Madrid, I asked if he likes math puzzles. “Yes,” he said. “But don’t you mean ‘enigmas’? When I hear ‘puzzle’ I tend to think of jigsaws.” I gave him this puzzle: There are three sisters who live together. Tell me their ages, based on the following bits of information: 1) Their ages multiply to 36. 2) The sum of their ages is the street number of their home. 3) Even if you knew the street number you wouldn’t be able to figure out their ages directly. 4) The oldest sister’s name is Monica.
“Well, the addition part won’t get me anywhere, but neither does knowing the girl’s name. I can just ignore these things, right?” my friend said. “Not a good idea,” I told him. He hasn’t found an answer yet; perhaps he’s still working it out.
As luck would have it, the gentleman living next door to me here in Berlin is also a Spaniard. Taking care to use what may be the preferred word in his language, I proposed an “enigma” to him, as well.
“Four people are being chased by zombies one night. They have to cross a bridge to escape. But the bridge is narrow and rickety, so they can only go two at a time. They can’t cross without a flashlight, but they only have one. Some of them are wounded, so they move at different speeds: The first can cross in one minute, the second in two, the third in four and the fourth in five. And the flashlight’s battery only lasts 12 minutes — which is exactly when the zombies will reach them. How can they all get across the bridge in time?”
My neighbor was stumped. “I can get them across in 13 minutes,” he said. “But you’ve only got 12,” I replied. “That’s what makes it an enigma. There is one way for all four people to escape the zombies.”
A couple of hours later there came a knock at the door. My neighbor had a solution, and it was the correct one. To reward his diligence and to foster good relations, I gave him a piece of candy. He grinned at the unexpected gesture.
I promised myself to keep telling puzzles. I’m not ready to talk to casual acquaintances about politics, but commenting on the weather is not very satisfying. Perhaps a brainteaser is just the ticket, neither too personal nor too distant.
Since then, my Spanish neighbor and I haven’t had time to talk, rushing past one another on various errands. But I have a feeling that he may have a puzzle for me. His smile is a bit broader now, and rather … enigmatic. (Tony László)