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!
This is a place. The first letter is after A and before Z but nowhere in between. You can bring as many people as you want, as long as they’re all dead. Where is it?
The cemetery. The letter C is after A and before Z, and it’s not found in the word “between”. The cemetery won’t take live ones. Fortunately I don’t speak from experience on that.
As a whole, I am both safe and secure.
Behead me, I become a place of meeting.
Behead me again, I am the partner of ready.
Restore me, I become the domain of beasts.
Stable. A table is a place of meeting. Able and ready is a common phrase, and a stable is where beasts reside (beasts of burden, not beasts like the one in Beauty and the Beast who lived in a glorious castle but the west wing was forbidden to enter until Belle…I’ve said too much!).
You must buy 100 chickens for exactly $100, and purchase at least one chicken from each store. The first store charges 5 cents/chicken, the second charges $1/chicken and the third charges $5/chicken. How many chickens should you buy from each store?
