Blue or red? – solution

(Read the problem here)


There are 13 blue balls.

If we take only one blue ball, the ball will be back to the box.

If we take two blu balls, both will be out from the box.

It means blue balls can not get out alone. Means there always at least one blue ball in the box.

So the remaining ball must be blue.



Heaven or hell – solution

(Read the problem here)


The woman should ask to anyone of them “Am I a woman?”

If the guard say “Yes”, then she just go to the door, but if the guard say “No”, then she choose the other door.


(…just for fun :))

Four captives – solution

(Read the problem here)




D and C can not see anyone, so it’s impossible for them to have any clue.

A can see B and C. Seeing B and C’s hat, A still not getting the answer, so A can not say anything.

B only can see C. But if B has the same colour as C, A must have know the answer and shout it already, but A don’t.

With this fact, B knows that A can’t know the answer only by seeing B and C, means B and C have different colour. Seeing C’s hat is red, B can conclude that B’s had is blue. So B can give the answer.



Four captives

Andy, Brian, Celline, and Drake were captivated by a very bad person, and were positioned as what can be seen in the picture below. All of them face a wall. Each of them was given a hat. No one of the four knows the colour of the hat that is wore by themselves, but they know that there are 2 red and 2 blue coloured hats.

The bad person told them that one of them have to name the colour of the hat him/herself wear. There’s only one chance. If the answer is wrong, all of them will be killed.


To save all of them who needs to give the answer and why?


Solution →
(better not open this if you don’t have any answers yet)