Here is a thinking puzzle that I've always enjoyed. Can you think of a place on the earth such that the following navigation can be done? You start from a point and travel 100 kilometers due south. Then you turn and travel 100 kilometers due east. Finally you turn again and travel 100 kilometers due north. You end up at the same place from which you started. Where did you start?
You are standing outside a room with a closed door. On the wall beside the door are three power switches, all off. You want to turn on the lamp inside the room but don't know which switch controls the lamp, and you can't see inside the room with the door closed. You can't tell if a switch controls anything else. Assuming that you can flip the switches any way you want, how would you tell which switch controls the lamp after you entered the room? No fair going back to reflip the switches after the door has been opened.
The emperor in an ancient Sumerian kingdom was a fair minded ruler who believed that he should give his condemmed prisoners one last chance to live. In this test the emperor had two baskets of stones. One basket had 100 black stones. The other basket had 100 white stones. The prisoner would be given the opportunity to redistribute all the stones between the two baskets any way the prisoner wanted. Afterwards, a blind priest would come out, pick one basket at random, then pick one stone from that basket at random. If the priest picked a white stone, the prisoner would live. If black, the execution would proceed as planned.
How should the prisoner divide up the stones in order to get the greatest probability of living?
All the stones must be divided between the two baskets.
The number of stones in each basket does not have to be the same.
Choosing The Best Salary
Assume you were offered a new job with a starting salary of $100,000.
You have a choice of two raise plans to choose from:
A) A raise of $2000 after every six months,
or B) A raise of $7000 after every year.
Which plan should you choose, A or B?
Assume that you plan to stay at this job for five years or more.
I'm sure you've taken one of those intelligence tests where they ask you to look at a series of objects and pick out the one that does not belong. The problem I have with those tests is that the "correct" solution depends on the perspective of the test author. I can usually find several valid answers. And even though I impugn that type of test, I did run across one example that I felt was very good.
From the series of five objects below, which one is unique? Choose the "best" answer.
You have a lighter and two fuses that take exactly one hour each to burn, but they don't burn at a steady rate.
For example, a fuse could burn slowly for the first half and then burn faster in the second half, for a total burn time of one hour. Or vice versa.
How would you use these two fuses to measure 45 minutes?
Melting Ice Cubes
A glass of water sits on a table with a few floating ice cubes.
When the ice has completely melted, will the level of the water in the glass have increased, decreased, or remain unchanged?
During WWII, there was a bridge connecting Germany and Switzerland, and on the German side, there was a sentry tower with a guard in it.
He would come out every three minutes to check on the bridge, and he had orders to turn back anyone who tried to get into Germany, and shoot anyone trying to escape without a pass.
There was a woman on the German side who desperately needed to get into Switzerland, and she knew she didn't have time to get a pass.
It would take her at least four minutes to cross the bridge, but she managed to do it.
The Deadly Choice
A political prisoner is condemned to death.
He can choose his execution method by selecting between three doors.
Through the first is a wide, deep pit full of sharp spikes.
Through the middle door is a room full of angry assassins with loaded guns.
Through the third is a room full of lions that haven't eaten in six months.
Which door is safest for him?
Glasses of Water
There are six glasses in a row.
The first three are full of water, and the next three are empty.
By moving only one glass,
how can you make them alternate between full and empty?
The Vanishing Leprechaun
Here's an old puzzle that has always intrigued me. Take a close look at the following two cartoon pictures. Notice that each picture is divided into three panels. The only difference between the upper picture and the lower one is the position of the top two panels. They've been swapped, left and right. Now count the leprechauns in each picture. Notice something strange? Better count them again just to be sure.
You might be tempted to say "The guy who's third from the right has disappeared." However, if you'll notice closely, he's just moved to the near center of the bottom picture, under the words "It's a".
So, which one has disappeared? And where did he go?
Click here for the explaination.
But don't spoil your fun by giving up too soon.
Click on the frogs to jump them over each other and get both groups to the other side.
A frog can move forward to an empty space, or jump one frog forward to an empty space.
See if you can figure this one out by yourself.
Sherlock Holmes and Dr Watson went on a camping trip. After a good meal and a bottle of wine, they lay down for the night and went to sleep. Some hours later Holmes woke up, nudged his faithful friend and said, "Watson, I want you to look up at the sky and tell me what you observe."
After a minute or so of pondering Watson said, Visually, I see thousands of stars. Astronomically, it tells me that there are millions of galaxies and potentially billions of planets. Astrologically, I observe that Saturn is in Leo. Chronologically, I deduce that the time is approximately a quarter past three in the morning. Meteorologically, I suspect that we will have a beautiful day tomorrow. Holmes, what does it tell you?"
Holmes was silent for about 30 seconds and said,
"Watson, you idiot! Someone has stolen our tent!"