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!
Find a single letter that replaces the first letter in the two words of each row to make two new words. What word is formed by combining the new letter of each row?
For example: PLANK _ BRISK
The new letter is F, making FLANK and FRISK. And F would be the first letter of the answer.
A man is running across a field at night clutching something in his arms as several other men pursue him. He looks back and sees they’re getting closer. In a final burst of effort his pursuers catch up and bring him crashing to the ground. His pursuers stand over him but do not touch him or take what he was carrying. Why not? Who was the running man?
Noon and midnight are both 12 o’clock and the Twelve Days of Christmas is a popular Christmas carol.
There are twelve face cards in a standard 52-card deck and twelve is the largest number with one syllable.
There are twelve steps in Alcoholics Anonymous, a troy pound is 12 ounces, there were 12 tribes of Israel and a popular movie was called, “Twelve Angry Men” (12 members of the jury). There are twelve function keys on your keyboard. F1 often shows a help screen and F5 reloads pages in your browser.
Many recipes measure items by the dozen, adding one more for a baker’s dozen. There are twelve months in a year.
It’s surprising how many times the number twelve shows up in our culture.