If 5 cats catch 5 mice in 5 minutes, how long will it take one cat to catch a mouse?

What does below pictogram mean?

The person who makes it has no need for it. He who purchases it does not use it. The person who does use it does not know they are. What is it?

The host of a game show, offers the guest a choice of three doors. Behind one is a expensive car, but behind the other two are goats.
After you have chosen one door, he reveals one of the other two doors behind which is a goat (he wouldn't reveal a car).

Now he gives you the chance to switch to the other unrevealed door or stay at your initial choice. You will then get what is behind that door.

You cannot hear the goats from behind the doors, or in any way know which door has the prize.

Should you stay, or switch, or doesn't it matter?

A landlord calls both of his sons and tells them that their horses will now decide who will transfer the inheritance. He tells them to race along the land till the end and the one whose horse will be slower will win and be the heir to all the property.

Both of them keep wandering for days but to no result. Then they ask a wise man regarding it. The man advises them on the matter after which they jump on the horses and race as fast as they can till the end. Why did they do it?

What did the wise man say?

In the picture given below, can you find out which digit will take place of the question mark?

Name a key which is hardest to turn.

What is the largest number you can write with just 3 digits?

Count the number of triangles in the picture below:

How can you leave a room with two legs and return with six legs?