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?

Place the numbers from 1 to 9 in the circles in a manner that each side of the triangle sums up to 17.

What two things can you never eat for breakfast?

My friends called me Iron59 because my parents are a chemist and a mathematician. What is my real name?

Suppose we lay down two cups in front of you. One of the cups is filled with tea and the other one with coffee. Now we ask you to take a spoonful of tea and mix it with the coffee. At this moment, the coffee cup has a mixture of tea and coffee. You have to take that mixture (spoonful) and add it back to the tea.

Can you now tell if the cup of coffee has more tea or the cup of tea has more coffee?

Which tank will fill first?

A man is surviving on an island along with his friend. They have been starving for four days for food. Suddenly, they find a fisherman. The friend goes with the fisherman in order to catch the fish (if they can find any).

The fisherman returns after some time but he is alone and has some salmon that he had prepared. When asked, the fisherman tells him that his best friend fell off the boat and drowned in the water. Starving for so long, he eats the meal while crying for his friend.

After being rescued, he goes to a diner and orders salmon. When he eats his meal, he jumps and commits suicide. Why did he do it?

A horse was tied to a rope 5 meters long and the horses food was 15 meters away from the horse. How did the horse reach the food?

Six glasses are in a row. The first three are filled with milk and the last three are empty. By moving only one glass, can you arrange them so that the full and the empty glasses alternate?

What goes up but never comes down?