A man lives on the fifteenth floor of an apartment building. Every morning he takes the elevator down to the lobby and leaves the building. In the evening, he gets into the elevator, and, if there is someone else in the elevator, or if it was raining that day, he goes back to his floor directly. Otherwise, he goes to the tenth floor and walks up five flights of stairs to his apartment. Can you explain why he does this?

Twenty frogs are sitting on a log floating on the surface of a river. Two of them decide to jump off into the water.

How many frogs are there on the log at this moment?

Out of the nine cats that you can see in the picture, there are only two that are completely identical. Can you find them out?

Can you solve this picture maths equation?

It belongs to you, but other people use it more than you do. What is it?

What is harder to catch the faster you run?

I am a three digit number.
My tens digit is five more than my ones digit.
My hundreds digit is eight less than my tens digit.
What number 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.

I look at you, you look at me I raise my right, you raise your left. What am I?

I have branches, but no fruit, trunk or leaves. What am I?