Find out the missing number in the picture attached:

What can go through glass without breaking it?

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?

A chess tournament is taking place on knock-out terms (the one who loses the match is out of the game).
(a) If 10 matches are played in total, how many players participated?
(b) If 20 players took part in the tournament, how many matches were played?

You need to arrange three 7 and mathematical symbols to form number 1?

A large container is kept in open under the rain. Every passing hour, the water collected inside the container becomes double what it was.

In ten hours, the container is filled completely. Can you calculate how long would it have taken to be filled in half?

I have one of the three numbers: 1, 2, or 3 in my mind. I speak only truth. You can ask me just one question for which I will only reply in yes or no or don't know. What question will you ask from me so that you are able to know the number?

They are the five precious gems of an everyday sort and all can be found on a Tennis Court. Who are they?

A man dies of old age on his 25 birthday. How is this possible?

Can you find the odd number in the following five choices?

1) 482636
2) 259807
3) 865195
4) 104739
5) 391744