Daily life puzzles

... if you are mathematician:)


There is father and son in a car. As it happens on the roads from time to time the have a terrible accident. They are both seriously injured and ambulances carry them to two different hospitals.

The son is on a surgery table while the surgeon walks in and says: „I can't do the surgery on him he is my son!"

How is it possible?

(assume relations are blood - no stepfather involved)

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You are standing next to three switches. You know these switches belong to three bulbs in a room behind a closed door – the door is tight closed, and heavy which means that it’s absolutely impossible to see if any bulb is on or not. All three switches are now in position off.

You can do whatever you want with the switches and when you are finished you open the door and go into the room. While in there you have to tell which switch belongs to which bulb.

How will you do that?

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Which direction is the bus going, left or right?

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Two men and women have shipwrecked on a deserted island. They are bored so they want to want to have some fun (sex). As there is a plenty of time each one of them wants to try all possible (heterosexual) partners.

The problem is that each of them has a different STD and if anyone was to catch another one he/she would hardly survive. They have two condoms that the men had brought. How are they supposed to plan they’re sexual activities so that every woman would have sex with every man and they would prevent spreading STD’s at the same time?

(Condoms are ideal, they last a lot but the used side can’t get to contact with the particular part of a different body)

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Mom is 21 years older than her son.

In 6 years she will be 5 times older than her son.

Where is the father right now?

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Parents buy cookies for their kids. They are saving money so they buy two discounted ones (few days after best before). They don’t want to look greedy so they also buy two cookies for the full price.

When they come home their two kids grab cookies, and each get two. They don’t check best before so their choice is random.

Do you think that life is fair and each kid gets one expired and one good cookie? Or one kid gets both expired? What is more likely to happen?

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Imagine you want to send a valuable item to your friend. You have big enough box on which you can place several padlocks. You both have enough padlocks but the problem is that you don’t have keys to padlocks of the other one.

How do you send the valuable item so that it doesn’t go unlocked? Sending just a key doesn’t help because someone could replicate it.

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Man comes home and what does he see? Mother-in-law came over.

I don’t know how but they started a fight. About what is not important at all.


Mother-in-law: You just lie all the time.

Man: No way...

Mother-in-law: You don’t tell a sentence without lying!

Man: Don’t be ridiculous!

Mother-in-law: Let’s try it: tell me one true sentence.

Man: Ok but you will get out after.

Mother-in-law: If you tell me true sentence I’ll go but if you will lie again I will stay. I promise I will!

Man thought for a while and than told her one sentence. Mother-in-law suddenly realized that to keep her promise she has to hang herself.

What did the man tell her?

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Five pirates stole a treasure – exactly hundred gold coins.

Pirates have a special way of dividing their loot:

  • The oldest one suggests how he would split up the loot.
  • Everyone votes.
  • If he gets more than half votes they split the loot according to his proposal.
  • If he doesn’t the others kill him and the process starts all over again – without the dead pirate.

All pirates are very used to this way of dividing and they never break the rules. Everyone’s top priority is his life. Second is money. And if there is no money or life involved in his decision he likes to harm the others.

How will they split the loot?

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Prison guards are bored so during dinner they announce the prisoners that they will play a game:

In the morning they will stand in a line so that every prisoner will see all standing in front of him but no one behind him. Guards will randomly paint red or white stripe on their back.

They will ask prisoners one by one from the last to the first. They will be allowed to say just one word “red” or “white”. If the prisoner says the color he has on his back he may go home in opposite case he will be executed without delay.

The prisoners are in one cell during the night and they can discuss the tactics.

Which is the best? How many will survive?

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If we tie a sheep to one peg it eats out a circle in grass. If we put a rope through a ring on its neck and tie both ends of the rope to two pegs it eats out an ellipse. If we want an oval we tighten one rope between two pegs put a ring with a rope on it and tie the sheep to its other end.

How to tie a sheep so that it eats out a square in grass? We have one sheep ropes pegs and rings.

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There are 32 red socks and 32 blue socks in the drawer. You can’t tell which sock is right and which is left. It’s dark and you are pulling socks out of the drawer. How many do you have to draw to be sure that you have a pair? (At least 2 socks of the same color)

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It takes 10 minutes to fry one steak - 5 minutes from each side. Two steaks can fit on a pan. What is the shortest possible time to fry 3 steaks?

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Two pitchers

You have two pitchers 5-liter and 3-liter (liter is approx. 2 pints) and unlimited supply of water. Can you measure out 4 liters?

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Where is the car?

There are three doors in front of you. New car waits behind one of them; goat is hidden behind each of the remaining two. You may open one of the doors and get what is behind them. You want the car off course. You choose your door. Moderator (who knows where the car is) than opens one of the remaining doors and shows that there is goat. Now he gives you the opportunity to change your decision.

You are standing in front of two closed doors. Will you change your decision?

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