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?

What has many keys but can’t open a single lock?

Solve the mathematical equation in the picture below.

When my father was 31 I was 8. Now he is twice as old as me. How old am I?

By including only four matchsticks in below picture, you have to make "Four Triangles And Two Squares"

Replace the question mark with the correct number.

2 + 2= 4
3 + 3= 18
4 + 4= 48
5 + 5= ?

An equation has been laid down using a few matchsticks. However, as you can see, the equation is not correct. Can you correct the equation if you are allowed to add or remove 5 matchsticks?

While preparing the table for dinner, wife came up with an idea to tease his mathematician husband. She asked her husband to pick nine toothpicks and make ten without breaking any toothpick.

The husband was also smart and did it within seconds. How ?

One absent-minded ancient philosopher forgot to wind up his only clock in the house. He had no radio, TV, telephone, internet, or any other means for telling time. So he travelled on foot to his friend's place a few miles down the straight desert road. He stayed at his friend's house for the night and when he came back home, he knew how to set his clock. How did he know?

There are five vowels (a, e, i, o, u) in the English language.
Can you tell us a word that contains all these vowels?