If I remove one from eleven it becomes Ten and if I remove one from nine also becomes Ten. How?

You knock a Table over in the library, and suddenly 20 eyes are looking at you.

What's a single-digit number with no value?

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 ?

People put me on the table and cut me but do not eat me. What am I?

Make eight squares by moving only two matchsticks.
Note- Square can be of different sizes.

When a clock is observed, the hour hand is at a minute mark and the minutes hand is six minutes ahead of it.

When the clock is observed again after some time, the hour hand is precisely on a different minute mark and the minute hand is seven minutes ahead of it.

Can you calculate how much time has elapsed between the two observations?

How many letters are in the alphabet?

You are presented with three boxes. One of them has a red ball inside and the other two have a black ball inside each of them. You are asked to pick up the one with red ball and you pick one. Now, one of the other boxes is opened and it is found to have a black ball.

You are presented with a chance to change your box with the one that is left closed. Will you change your box? Why or why not?

What is the difference between a jeweller and a jailer?