Here Come My Wife and Daughter

Two men are standing on one side of a bridge and two women are approaching them. One of the men says, "Here comes my wife and daughter" to which the second man replies, "Here comes my wife and daughter". If they have not married the same woman and the women aren't pregnant, how is this true?

Solution »

The men are widowers and married each others' daughter.

6 glasses in a row

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?

Solution »

Pour the water from the 2nd glass into the 5th glass.

What's wrong with this paragraph?

This is an unusual paragraph. I'm curious as to just how quickly you can find out what is so unusual about it. It looks so ordinary and plain that you would think nothing was wrong with it. In fact, nothing is wrong with it! It is highly unusual though. Study it and think about it, but you still may not find anything odd. But if you work at it a bit, you might find out. Try to do so without any coaching.

Solution »

The letter e, the most common letter in the English language, never appears in the entire paragraph

Prisoner's Probability to Live

You are a prisoner sentenced to death. The Emperor offers you a chance to live by playing a simple game. He gives you 50 black marbles, 50 white marbles and 2 empty bowls. He then says, "Divide these 100 marbles into these 2 bowls. You can divide them any way you like as long as you use all the marbles. Then I will blindfold you and mix the bowls and marbles up. You can then choose one bowl and remove one marble. If the marble is white, you live, but if the marble is black...you die.

How do you divide the marbles up so that you have the greatest probability of choosing a white marble?

Solution »

Place 1 white marble in one bowl, and place the rest of the marbles in the other bowl (49 whites, and 50 blacks).


This way you begin with a 50/50 chance of choosing the bowl with just one white marble and living. But even if you choose the other bowl, you still have an almost 50% chance of picking one of the 49 white marbles. There are no guarantees in life, but this is your best bet at surviving.

Two Guards

You're in a room with two doors. There's a guard at each door. One door is the exit, but behind the other door is something that will kill you. You're told that one guard always tells the truth and the other guard always lies. You don't know which guard is which. You are allowed to ask one question to either of the guards to determine which door is the exit. What question should you ask?

Solution »

Ask either guard what door the other guard would say is the exit, then choose the opposite door.


If you ask the guard who always tells the truth, he knows the other guard would lie, so he'll point you to the door leading to death. If you ask the guard who always lies, he knows the other guard would truthfully show you the exit, so he'll lie and point you to the door leading to death.

Three Daughters

I was visiting a friend one evening and remembered that he had three daughters. I asked him how old they were. "The product of their ages is 72," he answered. Quizzically, I asked, "Is there anything else you can tell me?" "Yes," he replied, "the sum of their ages is equal to the number of my house." I stepped outside to see what the house number was. Upon returning inside, I said to my host, "I'm sorry, but I still can't figure out their ages." He responded apologetically, "I'm sorry, I forgot to mention that my oldest daughter likes strawberry shortcake." With this information, I was able to determine all of their ages. How old is each daughter? You have enough information to solve the puzzle.

Solution »

3, 3, and 8. The only groups of 3 factors of 72 to have non-unique sums are 2, 6, 6 and 3, 3, 8 (both add up to 14). The presence of a single oldest child eliminates 2,6,6.

Twin Brothers

You are travelling down a road to a village. You reach a fork in the road and find a pair of identical twin brothers standing there. One of the brothers always tells the truth and the other always lies.

If you are allowed to ask only one question to one of the brothers to find which is the correct road to the village, what is your question ?

Solution »

Point to one of the roads in the fork and ask the following question to one of the brothers.

"If I ask your brother if this is the correct road to the village will he say yes or no?"

If he answers is "no" then it is the correct way to the village.

Think about it -

If the brother you are speaking to is the one who always lies, then he will say "no" as he knows that his brother who speaks the truth would anwser "yes". If the brother you are speaking to is the one who speaks the truth, he will say "no" as he knows that his brother will lie about it being the correct road. Either way an answer "no" tells you it is actually the right road. Similarly if you are pointing to the wrong road you will get the answer "yes".

One of the Eight Coins is Counterfeit

You are given eight coins and told that one of them is counterfeit. The counterfeit one is slightly heavier than the other seven. Otherwise, the coins look identical. Using a simple balance scale, can you determine which coin is counterfeit using the scale only twice?

Solution »

First weigh three coins against three others. If the weights are equal, weigh the remaining two against each other. The heavier one is the counterfeit. If one of the groups of three is heavier, weigh two of those coins against each other. If one is heavier, it's the counterfeit. If they have equal weight, the third coin is the counterfeit.

Ice Cube

A glass of water with a single ice cube sits on a table.

When the ice has completely melted, will the level of the water have increased, decreased or remain unchanged?

Solution »

Remain unchanged. When frozen, the ice cube displaces its weight.

Three Boxes of Black and White Marbles

Three closed boxes have either white marbles, black marbles or both, and they are labeled white, black and both. However, you're told that each of the labels are wrong. You may reach into one of the boxes and pull out only one marble. Which box should you remove a marble from to determine the contents of all three boxes?

Solution »

The one labeled both. Since you know it's labeled incorrectly, it must have all black marbles or all white marbles. After you determine what it contains, you can identify the other two boxes by the process of elimination.

4 Chains with 3 Links

You have four chains. Each chain has three links in it. Although it is difficult to cut the links, you wish to make a single loop with all 12 links. What is the fewest number of cuts you must make to accomplish this task?

Solution »

3 cuts. Cut each link in one chain. Separate them, and use the links to join the ends of the 3 intact chains.

Bucket

You have two buckets - one holds exactly 5 gallons and the other 3 gallons. How can you measure 4 gallons of water into the 5 gallon bucket?

(Assume you have an unlimited supply of water and that there are no measurement markings of any kind on the buckets.)

Solution »

1. Fill the 3-gallon bucket.
2. Pour the 3 gallons of water into the 5-gallon bucket
3. Fill the 3-gallon bucket again.
4. Fill up the 5-gallon bucket with the 3-gallon bucket, leaving you with 1 gallon left in the 3-gallon bucket.
5. Empty out the 5-gallon bucket.
6. Pour the remaining 1 gallon of water from the 3-gallon bucket into the 5-gallon bucket.
7. Fill the 3-gallon bucket.
8. Pour the 3 gallons of water from the 3-gallon bucket into the 5-gallon bucket leaving you with 4 gallons of water in the 5-gallon bucket.

Alternate solution:

1. Fill up the 5 gallon bucket
2. Pour it into 3 gallon bucket, leaving 2 gallons
3. Empty out the 3 gallon bucket
4. Pour the 2 gallons in the 5 gallon bucket into the 3 gallon bucket
5. Fill up the 5 gallon bucket and pour it into the 3 gallon bucket until it's full, leaving 4 gallons in the 5 gallon bucket.

Fuse Puzzle

You have a lighter and two fuses that take exactly one hour to burn, but they don't burn at a steady rate. For example, one fuse could take 59 minutes to burn the first inch and then burn the rest of the fuse in the last minute.

How would you use these two fuses to measure 45 minutes?

Solution »

Light the first fuse on both ends and the second fuse at only one end. When the first fuse burns out you know 30 minutes have passed. Light the other end of the second fuse and when it burns out, 45 minutes have passed.

Short Riddles 1

1. What seven-letter word has hundreds of letters in it?

2. What can run but never walks, has a mouth but never talks, has a head but never weeps, and has a bed but never sleeps?

3. What is full of holes but still holds water?

4. What is that goes up and goes down but does not move?

Solution »

1. Mailbox

2. A river

3. A sponge

4. Temperature

Short Teasers

1. If you had a ton of feathers and a ton of stones which would be heavier?

2. When can you add two to eleven and get one as the correct answer?

3. Tom's mother has three children. One is named April, one is named May. What is the third one named?

4. Two women apply for a job. They are identical. They have the same mother, father and birthday. The interviewer asks, "Are you twins?" to which they honestly reply, "No". How is this possible?

5. Mom and Dad have four daughters, and each daughter has one brother. How many people are in the family?

6. You're in a deep, dark jungle. You have a matchstick, a wooden stove, and a lantern. What will you light first?

Solution »

1. Neither. They both weigh a ton.

2. When adding time (11 AM + 2 Hours = 1 PM OR 11 PM + 2 Hours = 1 AM)

3. Tom

4. Because they were triplets.

5. Seven. The four daughters have only one brother, making five children, plus mom and dad.

6. Matchstick

The Prisoner

A prisoner is told "If you tell a lie we will hang you; if you tell the truth we will shoot you." What can he do to save himself?

Solution »

You will hang me.

Three Light Bulbs

You are standing outside a closed door. On the other side of the door is a room that has three light bulbs in it. The room is completely sealed off from the outside. It has no windows and nothing can get in or out except through the door. On the outside of the room there are three light switches that control each of the respective light bulbs on the other side of the door.

Your assignment is to determine which light switch controls which light bulb. You are allowed to enter the room only once, and once you come out, you must be able to state with 100% certainty which light switch controls which light bulb.

Solution »

Turn one light switch on, wait a few minutes, then turn it off and turn another light switch on. Go into the room and feel the light bulbs. The one that's still warm is connected to the switch that you first turned on, the one that is on was the second switch you turned on, and the last bulb is controlled by the switch that you didn't touch.

Sisters and Brothers

My daughter has many sisters. She has as many sisters as she has
brothers. Each of her brothers has twice as many sisters as brothers.
How many sons and daughters do I have?

Solution »

4 daughters and 3 sons.

For any particular daughter, she will have 3 sisters and 3 brothers. (DON'T count that daughter in -- she's the 4th girl -- otherwise it won't be 3 sisters = 3 brothers.)

But for any particular son, he will therefore have 4 sisters and 2 brothers. And 4 sisters are exactly twice as much as 2 brothers.

What is the next number in the sequence?

Here is a series of numbers. What is the next number in the sequence?

1
11
21
1211
111221
312211
13112221

Solution »

The next number in the sequence is 1113213211, because the rule for creating the next number is to simply describe the previous number. For example, you start of with 1, with is simply one 1, so the next number is 11. Now you have two 1's, so the next number is 21. Now you have one 2 and one 1, so the next number is 1211. The solution is to simply continue describing the previous number using only numbers.

Nine-minute Egg

You are a cook in a remote area with no clocks or other way of keeping time other than a four minute sandglass timer and a seven minute sandglass timer. (The kind you turn over - hourglass shaped) You do have a stove, however, with water in a pot already boiling. Somebody asks you for a nine-minute egg, and you know this person is a perfectionist and will be able to tell if you undercook or overcook the eggs by even a few seconds. What is the least amount of time it will take to prepare the egg? And how will you prepare it so that it is neither undercooked or overcooked?

Solution »

The answer is 9 minutes. First, flip both hourglasses over and drop the egg into the water. When the four minute timer runs out, flip it again. When the seven minute timer runs out, flip it over. The egg has been cooking seven minutes. Now when the four minute timer runs out again (after eight minutes) flip the seven minute timer back over. Since the seven minute timer has been running only a minute between flips, there's a minute worth of sand left. And when that minute runs out, the egg will have been cooking for exactly nine minutes.