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!
I’m built from anything you don’t like,
You’re using me right now in fact,
I am one but represent many,
When attacked I’m easily cracked,
I’m created in seconds but live forever
And though you may not understand,
I’ll help you do well but be careful my friend,
Hurt me and you won’t withstand.
Kids are often told, when dealing with unpleasant things, that it builds character. You’re reading the characters this riddle is written with. In computer science a char is often represented by one byte and can store any character you want.
When politicians have their character besmirched it can swiftly change the voting public’s mind about them. Characters in novels are created with a few lines but live on in our memories. And if your character or reputation is damaged, you may find it hard to deal with the aftermath.
And here’s a great quote from Warren Buffet on your character.
“It takes 20 years to build a reputation and five minutes to ruin it. If you think about that, you’ll do things differently.” — Warren Buffet
Kevin brings his school supplies to the counter. The cashier rings up his purchase for a total of $1.70. Kevin is puzzled, and says, “I bought 2 pencils at 2 cents each, 5 pencils at 4 cents each and 8 notebooks and 12 sheets of colored paper. I don’t remember the prices of the latter two, but the total can’t be $1.70.”