How can you take 2 from 5 and leave 4?

Can you count the number of matches in the picture below ?

Eight of us go fourth, not back, to protect our king from an attack. What are we?

A doctor and a boy were fishing. The boy was the doctor’s son, but the doctor was not the boy’s father. Who was the doctor?

We have two identical balls in terms of diameter and weight. However, one of them is solid and the other is hollow.

Without knocking the ball, can you find the solid ball?

How is the moon similar to a dollar?

100 prisoners are stuck in the prison in solitary cells. The warden of the prison got bored one day and offered them a challenge. He will put one prisoner per day, selected at random (a prisoner can be selected more than once), into a special room with a light bulb and a switch which controls the bulb. No other prisoners can see or control the light bulb. The prisoner in the special room can either turn on the bulb, turn off the bulb or do nothing. On any day, the prisoners can stop this process and say "Every prisoner has been in the special room at least once". If that happens to be true, all the prisoners will be set free. If it is false, then all the prisoners will be executed. The prisoners are given some time to discuss and figure out a solution. How do they ensure they all go free?

A beggar on the street can make one cigarette out of every 6 cigarette butts he finds. After one whole day of searching and checking public ashtrays the beggar finds a total of 72 cigarette butts. How many cigarettes can he make and smoke from the butts he found?

As easy as you can get into me, it is as hard to get out of me.

Do you know what I am?

You may enter, but you may not come in. I have space, but no room. I have keys, but open no lock. What am I?