Lucrezia Borgia invited a prospective victim to lunch. They ate a hearty meal of roast venison, with a selection of fresh vegetables, all washed down with the finest wine imported from Bordeaux, France.
After the meal, they ate figs and freshly picked grapes.
“Just one apple left”, said Lucrezia, “I insist you have it.
“No”, said the guest, “I couldn’t”.
“Tell you what”, said Lucrezia, “we’ll share it”, and promptly sliced the apple in two with her sharpest knife. The guest and Lucrezia started to eat their respective halves when the guest’s eyes rolled towards the ceiling and he fell over, dead.
“Another victim successfully dispatched,” thought Lucrezia.
Breath. Air is light, but even Stig Severinsen, the world record holder can only hold his breath for 22 minutes. The world’s strongest man can’t beat that, but you can have the pleasure of telling him to his face.
U2 has a concert that starts in 17 minutes and they must all cross a bridge to get there. All four men begin on the same side of the bridge. You must help them across to the other side. It is night. There is one flashlight. A maximum of two people can cross at one time. Any party who crosses, either 1 or 2 people, must have the flashlight with them.
The flashlight must be walked back and forth. It cannot be thrown and other tricks like that are not needed to solve the problem. The solution is simply a matter of allocating resources in a certain order. Each band member walks at a different speed. A pair must walk together at the rate of the slower man’s pace:
Bono: 1 minute to cross Edge: 2 minutes to cross Adam: 5 minutes to cross Larry: 10 minutes to cross
For example: if Bono and Larry walk across first, 10 minutes have elapsed when they get to the other side of the bridge. If Larry then returns with the flashlight, a total of 20 minutes have passed and you have failed the mission.
This is one of my favorite brain teasers and I want to give you the satisfaction of figuring it out on your own. If you’re having a hard time, here’s a hint: There is a valid answer that doesn’t require tricks like throwing the flashlight or shining it backwards or having some other means of moving the flashlight.
There’s an assumption people often make that keeps them from solving this. Two members cross the bridge each time, but neither one of the two who crossed necessarily need to return. Think about how that would be possible. If you’re still stuck, use objects to simulate their movements. Use whatever you have laying around – pens, paper, erasers – and move them back and forth. Good luck!