What's the only room from which no one can enter or leave

A pond had 60 fish, out of which, all but 20 died.
How many fishes are now present in that pond?

Distances from you to certain cities are written below.

BERLIN 200 miles

PARIS 300 miles

ROME 400 milesAMSTERDAM 300 miles

CARDIFF ??? miles

How far should it be to Cardiff ?

Name one eight-letter word with 'kst' in the middle, 'in' the beginning, 'and' at the end.?

If,

6 / 7 = 2
3 / 9 = 7
8 / 2 = 6

Then

4 / 5 = ?

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?

The doctor advised his patient to take a tablet after every fifteen minutes. He gave him five tablets in total.

How much time will he take to have all the five tablets?

In a kingdom, King George did not allow any citizen to visit the world outside. Also, only a person with proper paperwork was allowed to enter or he was sent back. A wooden bridge was what connected the kingdom to the world. The king had appointed a sharpshooter who would check the every five minutes on the bridge to check. After checking, he would go back to his hut and return exactly after five minutes again. The bridge took 9 minutes to cross.

A merchant was able to escape the kingdom without harming the shooter. How?

What has one eye, but can’t see?

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

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